SLOT-CONTROLLED 

AIRPORTS

FAA’s Rules Could be 

Improved to Enhance 

Competition and Use 

of Available Capacity

Report to the Committee on Commerce, 

Science, and Transportation, 

U.S. Senate

September 2012

GAO-12-902

United States Government Accountability Office

GAO
United States Government Accountability Office

Highlights of GAO-12-902, a report to the 

Committee on Commerce, Science, and 

Transportation, U.S. Senate 

September 2012

SLOT-CONTROLLED AIRPORTS 

FAA’s Rules Could Be Improved to Enhance 

Competition and Use of Available Capacity

Why GAO Did This Study

To help manage airport congestion, 

airlines operating at four U.S. 

airports—Washington’s Reagan 

National and the three major New York 

City area airports—must obtain 

operating authorizations called slots 

from FAA to take off or land. Airlines 

operating out of Reagan National also 

may not operate flights beyond a 

1,250-mile perimeter without 

congressional approval. In addition to 

the 24 flights (12 round trips) 

previously approved, Congress 

recently authorized 16 more beyondperimeter flights (8 round-trips) at 

Reagan National—flights that the 

airport authority fears will adversely 

affect Reagan National and the 

authority’s ability to continue servicing 

its debt. Some airlines seeking to 

serve slot-controlled airports assert 

that slot control rules cause the

airports to be underutilized or used 

inefficiently. GAO was asked to review 

(1) the effects of adding more beyondperimeter flights from Reagan National 

and (2) how well slot control rules are 

working to reduce congestion, while 

maximizing capacity and encouraging 

competition. GAO analyzed slot 

allocation and airline schedule data, 

developed a statistical model, and

interviewed FAA officials and others. 

What GAO Recommends

Among other things, GAO 

recommends that FAA improve its 

administration of the slot control rules, 

including applying the utilization 

requirement to individual slots. 

Department of Transportation (DOT) 

and FAA provided technical comments, 

which GAO incorporated as 

appropriate, and agreed to consider 

the recommendations.

What GAO Found

The 16 new beyond-perimeter flights that were authorized in 2012 for Reagan 

National Airport are likely to have a limited effect on the airports in the 

Washington, D.C., area. Reagan National has sufficient runway capacity to 

accommodate the new beyond-perimeter flights and, with some improvements to 

baggage handling and security screening facilities, will have sufficient terminal 

capacity. Reagan National is routinely operating below 67 hourly takeoffs and 

landings (“slots”)—the maximum number authorized in any one hour—mostly 

because general aviation or other unscheduled aircraft operations decreased 

substantially after new security restrictions were imposed following the 

September 11, 2001, terrorist attacks. GAO’s analysis found that the new 

beyond-perimeter flights could add a maximum of about 5 percent of 2011 

passenger levels at Reagan National, and if all of that increase came from 

passengers moving from Dulles International or Baltimore-Washington 

International Thurgood Marshall, these airports could experience a maximum 

decline of 4.1 percent of 2011 passenger levels. As a result, because Reagan 

National and Dulles generally do not share what are largely fixed costs, 

passengers shifting from Dulles to the new beyond-perimeter flights at Reagan 

National would, in the worst-case scenario, increase average airline costs to use 

Dulles by about 4 percent. Similarly, the new beyond-perimeter flights are not 

likely to affect the Washington Metropolitan Airports Authority’s (MWAA) ability to 

service its $5.2 billion debt for the two airports. Finally, because half of the new 

beyond-perimeter flights were awarded to low cost airlines, thereby increasing 

competition, these new flights could have a positive effect on airfares on routes 

where new flights were added. 

Slot control rules help the Federal Aviation Administration (FAA) manage 

congestion at these four airports by limiting the number of takeoffs and landings 

that airlines may make per hour. The rules, however, in effect, allow some 

existing airport capacity to go unused, and this capacity is therefore unavailable

to other airlines because airlines are not required to schedule a flight for each of 

their slots, but instead are only required to use their slots 80 percent of the time. 

Moreover, FAA’s recordkeeping and its process for reviewing airlines’ selfreported slot utilization data do not provide sufficient assurance that FAA can 

identify instances when airlines do not meet the 80 percent utilization 

requirement or determine how much capacity is going unused. In addition, FAA’s

allowing airlines to apply the requirement collectively to their pool of slots, rather 

than individual slots, further contributes to slots going unused and provides an 

advantage to airlines with large slot holdings. In addition to some existing 

capacity going unused, flights at the slot-controlled airports, even when operated, 

tend to be scheduled in such a way that available capacity is used more 

inefficiently than at like-sized airports that are not slot-controlled, thereby limiting 

passenger growth and access by new-entrant airlines that could offer new 

service or lower fares. For example, GAO found that flights operated at slotcontrolled airports tend to be scheduled with smaller aircraft. Using statistical 

analyses, GAO found that scheduled passenger flights at slot-controlled airports 

are 75 percent more likely to be scheduled by airlines using an aircraft with fewer 

than 100 seats than flights at other like-sized airports that are not slot-controlled. 

Slot-controlled airports also tend to have certain routes that are flown at higher 

daily rates and aircraft that are less full.

View GAO-12-902. For more information, 

contact Susan Fleming at (202) 512-2834 or 

flemings@gao.gov
Page i GAO-12-902 Airport Slot Controls

Letter 1 

Background 4

Reagan National Can Accommodate New Beyond-Perimeter 

Flights, Which Are Likely to Have a Limited Effect on Other 

Washington, D.C., Area Airports 16

Slot Control Rules Help Manage Congestion, but Allowing Airlines 

Not to Use Some Slots May Hinder Competition 29

Conclusions 53

Recommendations for Executive Action 54

Agency Comments and Our Evaluation 55

Appendix I Objectives, Scope, and Methodology 58

Appendix II Comparative Information on Major Airports in the New York City and 

Washington, D.C., Area 64

Appendix III History of Slot Control Rules and Related Actions 65

Appendix IV Trends in Average Annual Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports 75

Appendix V Logistic Regression Analysis of Slot-Controlled Airports and 

Aircraft Size 99

Appendix VI Comments from the Metropolitan Washington Airports Authority 107

Appendix VII Comments from the Port Authority of New York and New Jersey 111

Contents
Page ii GAO-12-902 Airport Slot Controls

Appendix VIII GAO Contact and Staff Acknowledgments 112

Tables

Table 1: Selected Slot Control Rule Provisions for the Four U.S. 

Slot-Controlled Airports 10

Table 2: Hourly Aircraft Operations (Takeoffs and Landings) 

Allowed at Reagan National 17

Table 3: Impact of New Beyond-Perimeter Exemptions on Average 

Peak and Non-Peak Hour Slot Allocations at Reagan 

National for the Summer 2012 Season 18

Table 4: Projected Impact of the New Beyond-Perimeter Flights at 

Reagan National on the Cost per Enplaned Passenger in 

2013 and 2014 25

Table 5: Percentage Difference in Flights at Slot-Controlled 

Airports That Use Small Aircraft Compared with Flights at 

Non-Slot-Controlled Airports, 2011 42

Table 6: Percentage Difference in Likelihood of a Flight’s Using 

Small Aircraft at Slot-Controlled Airports Compared with 

Non-Slot-Controlled Airports 44

Table 7: Logistic Regression Results for Slot-Controlled-Airport and 

Aircraft-Size Model, Small Aircraft with 100 Seats or Fewer 104

Table 8: Logistic Regression Results for Alternative SlotControlled-Airport Variable Definitions, Small Aircraft 

with 100 Seats or Fewer 104

Table 9: Logistic Regression Results for Alternative SlotControlled-Airport Variable Definitions, Small Aircraft 

with 124 Seats or Fewer 105

Table 10: Logistic Regression Results for Alternative SlotControlled-Airport Variable Definitions, Small Aircraft 

with 80 Seats or Fewer 106

Figures

Figure 1: Annual Percentage of Late Arrivals and Flight 

Cancellations at the Four Slot-Controlled Airports 

Compared with All Airports from 2002 through 2011 6

Figure 2: Nonstop Beyond-Perimeter Slot Exemption Destinations 

from Reagan National from 2000 through 2012 15

Figure 3: Areas of Unused Capacity at Slot-Controlled Airports 32
Page iii GAO-12-902 Airport Slot Controls

Figure 4: Airports’ Share of Scheduled Flights to or from the Same 

Destination by the Same Airline within 15 Minutes or 30 

Minutes of One Another, February 2011 47

Figure 5: Average Load Factors at Large Hub Airports for 

Scheduled Flights during 2011 48

Figure 6: Proportion of Legacy and Other Airline Passenger Traffic 

at Slot-Controlled and Non-Slot-Controlled Large Hub 

Airports, 2011 50

Figure 7: Timeline of Major Actions Taken Regarding Slot Controls 

and Perimeter Rules at the Major New York City Area 

Airports and Reagan National 66

Figure 8: Indexed Average Passenger Traffic for All BWI Domestic 

Flights and Flights between BWI and Denver International 

Airport, 2000 to 2011 75

Figure 9: Indexed Average Annual Airfare for All BWI Domestic 

Flights and Flights between BWI and Denver International 

Airport, 2000 to 2011 76

Figure 10: Indexed Average Annual Passenger Traffic for All BWI 

Domestic Flights and Flights between BWI and Las Vegas 

McCarran International Airport, 2000 to 2011 77

Figure 11: Indexed Average Annual Airfares for All BWI Domestic 

Flights and Flights between BWI and Las Vegas McCarran 

International Airport, 2000 to 2011 78

Figure 12: Indexed Average Passenger Traffic for All BWI Domestic 

Flights and Flights between BWI and Los Angeles 

International Airport, 2000 to 2011 79

Figure 13: Indexed Average Annual Airfares for All BWI Domestic 

Flights and Flights between BWI and Los Angeles 

International Airport, 2000 to 2011 80

Figure 14: Indexed Average Passenger Traffic for All BWI Domestic 

Flights and Flights between BWI and Phoenix Sky Harbor 

International Airport, 2000 to 2011 81

Figure 15: Indexed Average Airfares for All BWI Domestic Flights 

and Flights between BWI and Phoenix Sky Harbor 

International Airport, 2000 to 2011 82

Figure 16: Indexed Average Passenger Traffic for All BWI Domestic 

Flights and Flights between BWI and Salt Lake City 

International Airport, 2000 to 2011 83

Figure 17: Indexed Average Airfares for All BWI Domestic Flights 

and Flights between BWI and Salt Lake City International 

Airport, 2000 to 2011 84
Page iv GAO-12-902 Airport Slot Controls

Figure 18: Indexed Average Passenger Traffic for All BWI Domestic 

Flights and Flights between BWI and Seattle-Tacoma 

International Airport, 2000 to 2011 85

Figure 19: Indexed Average Airfares for All BWI Domestic Flights 

and Flights between BWI and Seattle-Tacoma 

International Airport, 2000 to 2011 86

Figure 20: Indexed Average Passenger Traffic for All Dulles 

Domestic Flights and Flights between Dulles and Denver 

International Airport, 2000 to 2011 87

Figure 21: Indexed Average Airfares for All Dulles Domestic Flights 

and Flights between Dulles and Denver International 

Airport, 2000 to 2011 88

Figure 22: Indexed Average Annual Passenger Traffic for All Dulles 

Domestic Flights and Flights between Dulles and Las 

Vegas McCarran International Airport, 2000 to 2011 89

Figure 23: Indexed Average Annual Airfares for All Dulles 

Domestic Flights and Flights between Dulles and Las 

Vegas McCarran International Airport, 2000 to 2011 90

Figure 24: Indexed Average Annual Passenger Traffic for All Dulles 

Domestic Flights and Flights between Dulles and Los 

Angeles International Airport, 2000 to 2011 91

Figure 25: Indexed Average Annual Airfares for All Dulles 

Domestic Flights and Flights between Dulles and Los 

Angeles International Airport, 2000 to 2011 92

Figure 26: Indexed Average Annual Passenger Traffic for All Dulles 

Domestic Flights and Flights between Dulles and Phoenix 

Sky Harbor International Airport, 2000 to 2011 93

Figure 27: Indexed Average Annual Airfares for All Dulles 

Domestic Flights and Flights between Dulles and Phoenix 

Sky Harbor International Airport, 2000 to 2011 94

Figure 28: Indexed Average Annual Passenger Traffic for All Dulles 

Domestic Flights and Flights between Dulles and Salt 

Lake City International Airport, 2000 to 2011 95

Figure 29: Indexed Average Airfares for All Dulles Domestic Flights 

and Flights between Dulles and Salt Lake City 

International Airport, 2000 to 2011 96

Figure 30: Indexed Average Annual Passenger Traffic for All Dulles 

Domestic Flights and Flights between Dulles and SeattleTacoma International Airport, 2000 to 2011 97

Figure 31: Indexed Average Annual Airfares for All Dulles 

Domestic Flights and Flights between Dulles and SeattleTacoma International Airport, 2000 to 2011 98
Page v GAO-12-902 Airport Slot Controls

Abbreviations

AIR-21 Wendell H. Ford Aviation Investment and Reform Act for

 the 21st Century

BWI Baltimore Washington International Thurgood Marshall

 Airport 

BTS Bureau of Transportation Statistics

DOJ Department of Justice

DOT Department of Transportation 

IATA International Air Transport Association

FAA Federal Aviation Administration

JFK John F. Kennedy International Airport

MWAA Metropolitan Washington Airports Authority

TSA Transportation Security Administration

This is a work of the U.S. government and is not subject to copyright protection in the 

United States. The published product may be reproduced and distributed in its entirety 

without further permission from GAO. However, because this work may contain 

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Page 1 GAO-12-902 Airport Slot Controls

United States Government Accountability Office 

Washington, DC 20548

September 13, 2012

The Honorable John D. Rockefeller IV

Chairman

The Honorable Kay Bailey Hutchison

Ranking Member

Committee on Commerce, Science, and Transportation

United States Senate

For each takeoff or landing at Ronald Reagan Washington National 

Airport (Reagan National) and the three major New York City area 

airports—John F. Kennedy International (JFK), LaGuardia International 

(LaGuardia), and Newark Liberty International (Newark)—airlines must 

obtain an operating authorization, also known as a “slot,”1 from the 

Federal Aviation Administration (FAA). Although more than 150 airports 

are slot-controlled throughout the world, including all major European 

airports, only these four airports are currently subject to slot controls in 

the United States. FAA started limiting the number of takeoffs and 

landings per hour at these airports more than 40 years ago because of 

congestion and delay. Reagan National is also subject to a federallyimposed 1,250-mile limit on the distance of nonstop flights to and from the 

airport, called the perimeter rule. However, on three occasions since 

2000, federal statutes have been enacted requiring a total of 40 slot 

exemptions (20 round trips) to the perimeter rule, allowing nonstop flights 

to destinations more than 1,250 miles from the airport. This includes 16 

more beyond-perimeter flights (8 round trips) required as part of the 

reauthorization of FAA in February 2012.2 Although we reported in 1999 

and 20073

 

1

FAA regulations at 14 C.F.R. Part 93, subparts K and S applicable to Reagan National 

Airport use the term “slots,” whereas FAA orders applicable to JFK, LaGuardia, and 

Newark use the term “operating authorization.” For the purposes of this report we refer to 

both as slots.

that Reagan National could accommodate additional flights, 

the airport authority that operates Reagan National—the Metropolitan 

2

FAA Modernization and Reform Act of 2012, Pub. L. No. 112-95, § 414, 126 Stat. 11 

(2012).

3

GAO, Reagan National Airport: Capacity to Handle Additional Flights and Impact on 

Other Airports, GAO/RCED-99-234 (Washington, D.C.: Sept. 17, 1999) and Reagan 

National Airport: Update on Capacity to Handle Flights and Impact on Other Airports, 

GAO-07-352 (Washington, D.C.: Feb. 28, 2007).

 
 

Page 2 GAO-12-902 Airport Slot Controls

Washington Airports Authority (MWAA)—raised concerns about the 

airport’s ability to accommodate these new beyond-perimeter flights as 

well as their effect on the other Washington, D.C., area airports and the 

ability of MWAA to continue servicing its $5.2 billion debt.

The New York City area airports are operating under temporary FAA 

orders, which constitute the current slot control rules that limit the number 

of takeoffs and landings for flights out of those airports. However, despite 

operating under slot control rules, these airports continue to be among 

the most delayed in the country, which in turn affects the efficiency of the 

nation’s entire airspace system. Moreover, although the rules were 

designed to control congestion, while also maximizing the available 

airport capacity, some airlines seeking entry into these airports assert that 

the current rules do not adequately address inefficient uses of the 

constrained airspace and airport capacity, and that not enough of existing 

capacity is allocated to new entrants, restricting competition and access 

to the primary commercial airports in the region. They also assert that 

airlines currently operating out of these airports use their slots in ways 

that keep out competitors. To address these problems at the New York 

City area airports, FAA, which is responsible for managing congestion at 

airports, tried to implement rules in 2006 (that were revised in 2008) that, 

among other things, would have allowed FAA to auction some slots held 

by incumbents and, under one of the two options, keep the proceeds. In 

October 2009, before implementing any changes, FAA rescinded the final 

congestion management rules for the New York City area airports, in 

general, citing congressional and airline opposition to auctioning slots, 

among other things, and a federal court ruling.4

 

4

74 Fed. Reg. 52132 (Oct. 9, 2009); 74 Fed. Reg. 52134 (Oct. 9, 2009). The federal court 

ruling was an order by the United States Court of Appeals for the District of Columbia 

Circuit. Port Authority of New York and New Jersey v. Federal Aviation Administration, 

Court of Appeals for the District of Columbia, Order No. 08-1329 (Dec. 8, 2008).

In 2010, the Department 

of Transportation (DOT) began developing a “Slot Management and 

Transparency” rule for JFK, LaGuardia, and Newark to replace the 

temporary slot control rules under which they have been operating since 

2006 for LaGuardia and since 2008 for JFK and Newark. These 

temporary rules have been extended twice, creating a level of uncertainty 

in the market about when the final rule will be issued and what it will 

contain.
 

Page 3 GAO-12-902 Airport Slot Controls

In response to your request, we reviewed the potential effects of 

increasing the number of beyond-perimeter slot exemptions at Reagan 

National and whether slot control rules at the four U.S. slot-controlled 

airports are working to reduce congestion, while maximizing available 

capacity and encouraging competition. 

To review the potential effects of increasing the number of beyondperimeter slot exemptions at Reagan National, we

• compared the airport’s airside capacity assessment with actual usage;

• reviewed terminal space needs;

• assessed the effects of the additional beyond-perimeter flights on 

security screening wait times, passenger traffic, capital financing, and 

aircraft noise; and

• interviewed officials from FAA, MWAA—which operates Reagan 

National and Dulles International Airport (Dulles)—and BaltimoreWashington International Thurgood Marshall Airport (BWI) as well as 

representatives from airlines and others.

To review whether slot controls at U.S. slot-controlled airports are working 

to reduce congestion while maximizing available capacity and 

encouraging competition, we compared and contrasted DOT data on 

flight delays, as well as airline schedule data on aircraft size, flight 

frequency, and other factors at slot-controlled airports with airports that 

are not slot-controlled. We also constructed a statistical model to assess 

whether flights at the slot-controlled airports are maximizing passenger 

throughput as compared with other large hub airports5

 

5

Federal law defines large hub airports as those commercial service airports that have at 

least 1 percent of the passenger boardings. 49 U.S.C. § 40102(29).

that are not slotcontrolled by examining aircraft size. We reviewed the reliability of the 

data used in our analyses and concluded that they were sufficiently 

reliable for our purposes. We also interviewed officials from DOT, FAA, 

the Department of Justice (DOJ), MWAA, and the Port Authority of New 

York and New Jersey, which operates the New York City area airports, 

and interviewed representatives from airlines and others. We conducted 

this performance audit from October 2011 to September 2012 in 

accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audits to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objective. We believe that 
 

Page 4 GAO-12-902 Airport Slot Controls

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives. More details about our scope 

and methodology of our work are presented in appendix I.

The Washington, D.C., region and New York City area airports vary with 

regard to their size, proximity to downtown areas, and type of service 

provided. In the Washington, D.C., region, Reagan National is located in 

Arlington County, Virginia, near the nation’s capital, while the two other 

major airports—Dulles and BWI—that are part of the Washington, D.C., 

area air passenger market are larger and located farther from city 

centers. While Reagan National and BWI primarily provide domestic 

service, about one-fourth of enplanements at Dulles in 2011 were 

international. Reagan National and Dulles are owned by the federal 

government and are operated by MWAA under a 50-year lease that has 

been extended 30 years (1987-2067). Reagan National is subject to slot 

controls, but Dulles and BWI are not. In the New York City area, 

LaGuardia is located in Queens, near Manhattan, and primarily provides 

domestic air service, while JFK and Newark are larger airports that are 

located farther from Manhattan and provide more international service.

Appendix II provides more detailed comparative information about the 

four slot-controlled airports, plus Dulles and BWI.

On-time flight performance at Reagan National is comparatively better 

than the other slot-controlled airports and cancellations and delays at the 

New York City area airports have been among the worst in the nation.

According to on-time arrival performance data that airlines reported to the 

Bureau of Transportation Statistics (BTS) for 2011, among 29 major 

airports,6

 

6

BTS defines these airports as those within the continental United States that enplaned 1 

percent or more of the domestic scheduled-service passengers as of June 2010. Federal 

law defines large hub airports as those commercial service airports that have at least 1 

percent of the passenger boardings. 49 U.S.C. § 40102(29). 

Reagan National ranked 22nd, JFK ranked 25th, LaGuardia 

ranked 27th, and Newark ranked 29th. Because, according to FAA, onethird of the approximately 50,000 aircraft that FAA guides through the 

national airspace system every day move through the New York area at 

some point during a typical day, delays in this region can have a 

disproportionate impact on airspace and airport delays experienced 

throughout the rest of the system. According to 2012 research conducted 

by the MITRE Corporation for FAA, one-third of the flights in the country 

Background
 

Page 5 GAO-12-902 Airport Slot Controls

are directly affected by delays in the New York City and Philadelphia 

areas. Furthermore, the rate of late arrivals and flight cancellations—

another indicator of on-time performance—at the three New York City 

area airports was worse than the system-wide average during the last 10 

years.7

 

7

The data indicated that the cancellation rate at LaGuardia was generally twice the 

system-wide average during this period. See also GAO, National Airspace System: DOT 

and FAA Actions Will Likely Have a Limited Effect on Reducing Delays during Summer 

2008 Travel Season, 

The rate of late arrivals and cancellations at Reagan National, 

however, was better than the system-wide average during 4 of the 10 

years (see fig 1). 

GAO-08-934T (Washington, D.C.: July 15, 2008).
 

Page 6 GAO-12-902 Airport Slot Controls

Figure 1: Annual Percentage of Late Arrivals and Flight Cancellations at the Four Slot-Controlled Airports Compared with All 

Airports from 2002 through 2011

Note: In this figure, the percentage of delays and cancellations has been combined. The system-wide 

data include the four slot-controlled airports. Flights that arrived 15 minutes or more late compared 

with the scheduled time are counted as late arrivals. BTS data do not include international flights, 

which represented about half of the enplanements at JFK and about one-third of the enplanements at 

Newark in 2011. 

FAA previously relied on its statutory authority to manage airspace usage 

to implement slot controls through an FAA regulation called the High 

Density Rule, which capped the number of hourly arrivals and departures 

permitted at five designated “high density traffic airports”—LaGuardia, 

JFK, Newark, Washington National,8

 

8

In 1998, Washington National Airport was renamed Ronald Reagan Washington National 

Airport. 

and Chicago O’Hare International—
 

Page 7 GAO-12-902 Airport Slot Controls

and, among other things, required airlines to obtain slots for these 

operations. The High Density Rule was implemented at Reagan National 

and the three New York City area airports in the late 1960s to reduce 

congestion and delay. Reagan National has remained slot-controlled 

under the High Density Rule since 1969, although there have been 

modifications to the operating limits and provisions of the rule throughout 

the years. On the other hand, rules at the New York City area airports 

have at times been relaxed or suspended as a result of statutory changes 

and FAA actions. For example, because of lessened concerns about 

congestion at Newark, FAA suspended slot controls at that airport from 

1970 through 2008. In addition, in the 1990s, there was some perception 

that slot controls were a barrier to improved service, in part, because new 

airlines were unable to establish service at the slot-controlled airports. 

Subsequently, in 2000, the Wendell H. Ford Aviation Investment and 

Reform Act for the 21st Century required the High Density Rule to be 

phased out at JFK and LaGuardia by January 1, 2007. These 2000 

statutory provisions also directed DOT, in the interim, to grant exemptions 

to the High Density Rule to allow for a limited number of flights operated 

by new entrant airlines and for flights serving small communities. As a 

result, airlines scheduled more flights at LaGuardia than the airport could 

handle without unreasonable delays. FAA subsequently issued temporary 

orders limiting scheduled operations at LaGuardia to 75 per hour in 2006 

and at JFK and Newark to 81 per hour in 2008.9

Before FAA adopted slot allocation and transfer rules, in 1985, airlines 

organized scheduling committees through which slots were allocated. In 

1986, FAA, believing a secondary market in slots would address 

concerns by new entrant airlines and smaller carriers about access to and 

competition at High Density Rule-controlled airports, amended the rule to 

The limits at LaGuardia 

were based on the limits prior to the 2007 phase-out. In setting the limits 

on scheduled operations at JFK and Newark, FAA undertook an analysis 

that included modeling the estimated level of delay associated with 

various levels of operations. (As shown in fig. 1, from 2002 through 2011, 

the rate of late arrivals and flight cancellations at the slot-controlled 

airports and system-wide was greatest in 2007 when slot controls were 

not in effect at JFK and Newark.)

 

9

In 2009, FAA reduced the operating limits at LaGuardia to 71 scheduled operations per 

hour to improve operational efficiency. The current slot allocations were kept, but any slots 

returned to FAA, withdrawn for non-use, or unallocated during each affected hour would 

be retired until the number of slots in that hour reaches 71.
 

Page 8 GAO-12-902 Airport Slot Controls

allow airlines to buy and sell slots. Under the temporary orders at the New 

York City area airports, imposed after the statutory expiration of the High 

Density Rule at JFK and LaGuardia, FAA allocated slots to airlines based 

on their current operating schedules at those airports in conjunction with 

voluntary airline schedule-reduction agreements or, in the case of 

LaGuardia, based on their current slot or slot exemptions holdings. To 

encourage competition at these airports under the High Density Rule, 

Congress also has periodically directed DOT to allocate slots exemptions 

to airlines operating new service at slot-controlled airports. Generally, 

once airlines have been allocated slots or slot exemptions, so long as 

they comply with the rules, they may keep them indefinitely10 and 

consider them to be valuable assets.11

Although slot controls were designed to manage congestion by limiting 

the number of scheduled flight operations per hour at each of these 

airports, the rules also contain a provision designed to encourage use of 

airport capacity by requiring airlines to use their slots a minimum 

percentage of the time. Beginning in 1986, FAA’s High Density Rule 

required airlines at specified airports to use their slots at least 65 percent 

of the time, but starting in 1992, they were required to use them at least 

80 percent of the time. Although the 80 percent usage requirement is 

applicable to all four slot-controlled airports, other provisions of the rules 

differ between the airports, including

• the hours when airlines are required to have a slot to operate a flight,

• the time periods for which slots usage is measured and reported to 

FAA, and

• whether airlines can buy or sell slots (see table 1).

In general, at Reagan National and LaGuardia, slots are allocated for 

every day of the week and must be used at least 80 percent of time in a 

fixed, 2-month reporting period (e.g., January-February, March-April, 

 

10Slots are subject to FAA withdrawal, for example, if a slot is not used at least 80 percent 

of the time over the applicable time period. In addition, slots are subject to FAA withdrawal 

at any time to meet operational needs such as reduced airport capacity.

11Although airlines consider slots to be valuable assets, FAA slot regulations at 14 C.F.R. 

§ 93.223(a), for example, provide that slots do not represent a property right but represent 

an operating privilege subject to absolute FAA control. The FAA slot regulations applicable 

to Reagan National also provide, in general, that slots may be bought, sold, leased, or 

traded for slots at other slot controlled airports. 14 C.F.R. § 93.221(a).
 

Page 9 GAO-12-902 Airport Slot Controls

etc.).12 At JFK and Newark, slots are allocated for a specific day of the 

week and must be used at least 80 percent of the time for that day during 

a scheduling season.13 Slots not used in accordance with the 80 percent 

rule are subject to withdrawal by FAA. Additionally, because the slot rules 

at the New York City area airports are contained in temporary FAA orders 

and are not considered by FAA to be a long-term solution, slots may not 

be bought or sold at those airports.14

 

12Under FAA’s temporary order applicable to LaGuardia, slots are not allocated on 

Saturdays. 

Slots may be leased and traded, 

however, at any of the slot-controlled airports.

13The summer season runs from the fourth Sunday in March to the fourth Saturday in 

October. The winter season runs from the fourth Sunday in October to the fourth Saturday 

in March.

14See, e.g., 73 Fed. Reg. 3510, 3513-14 (Jan. 18, 2008). In comparison to the temporary 

FAA orders in place at the New York City area airports, the FAA High Density Rule 

regulations applicable to slots at Reagan National provide, in part, that except as 

otherwise provided, slots may be bought, sold, or leased. 14 C.F.R. § 93.221. The major 

exception to this regulation at Reagan National is that slot exemptions may not be bought, 

sold, leased, or otherwise transferred, except through an air carrier merger or acquisition. 

49 U.S.C. 41714(j).
 

Page 10 GAO-12-902 Airport Slot Controls

Table 1: Selected Slot Control Rule Provisions for the Four U.S. Slot-Controlled 

Airports

Reagan 

National LaGuardia JFK Newark

Minimum slot 

usage 

requirement

80 percent 80 percent 80 percent 80 percent

Hours that 

airport is slotcontrolled

All hours 6:00 a.m. to 

9:59 p.m., 

Eastern Time, 

Monday – 

Friday and 

12:00 p.m. to 

9:59 p.m., 

Eastern Time, 

Sunday

6:00 a.m. to 

10:59 p.m., 

Eastern Time, 

daily

6:00 a.m. to 

10:59 p.m., 

Eastern Time, 

daily

Usage 

measured for... 

All days over 2-

month reporting 

period

All days over 2-

month reporting 

period

Each day of the 

week over a 

scheduling 

season

Each day of 

the week over 

a scheduling 

season a

Authorization 

to buy or sell 

slots

a

Allowed Not authorized Not authorized Not authorized

Authorization 

to lease or 

trade slots

Allowed Allowed Allowed Allowed

Source: FAA and FAA regulations

a

Slots that are not operated because the airline returned them to FAA prior to that season’s return 

deadline are not counted as unused for purposes of measuring slot usage. Airlines can return to FAA 

slots during periods of a season that the airline does not intend to operate. 

According to FAA officials, the differences in the rules for each airport are 

largely a product of history. For example, when FAA replaced the High 

Density Rule with temporary limitations on flight operations at LaGuardia 

in 2007, it adopted most of the rule’s provisions including, most 

importantly, the slot caps. Long-term changes were expected through a 

proposed rule issued by FAA in the summer of 2006. Additionally, 

according to an FAA official and International Air Transport Association 

(IATA) representatives, because JFK and Newark support a large number 

of international operations, the rules for those airports are more 

consistent with IATA’s Worldwide Slot Guidelines. These guidelines 

contain slot processes and policies for slot-controlled airports to facilitate 

international operations to or between other slot-controlled airports 

around the world.
 

Page 11 GAO-12-902 Airport Slot Controls

FAA and DOT’s Office of the Secretary share responsibility for managing 

slot control issues. FAA is responsible for administering the slot rules, 

which primarily includes slot allocation, transfers, and monitoring and 

enforcing airlines’ compliance with the 80 percent slot usage requirement. 

DOT’s Office of the Secretary is responsible for awarding within-perimeter 

and beyond-perimeter slot exemptions at Reagan National and 

monitoring competitive aspects of the airlines’ slot holdings. 

In 2006, FAA proposed a congestion management rule for LaGuardia that 

would limit operations, encourage the use of larger aircraft, and assign 

rolling expiration dates for slots. That notice of proposed rulemaking was 

withdrawn and superseded in 2008 by congestion management rules at 

JFK, LaGuardia, and Newark that would have created a market by 

annually auctioning a limited number of slots in each of the first 5 years of 

the rule, which had a 10-year term. In October 2009, before the terms of 

the 2008 rules became effective, FAA rescinded the rules citing, among 

other things, that the rulemakings had been highly controversial, and a 

court challenge that resulted in a December 2008 stay of the rules by the 

United States Court of Appeals for the District of Columbia Circuit. In 

addition, because of the complexity of the issues, the impact of an 

Omnibus Appropriations Act, 2009 provision,15

 

15Pub. L. No. 111-8, Division I, Title I, §115, 123 Stat. 524, 921 (2009). The Omnibus 

Appropriations Act, 2009 contained a provision prohibiting the Secretary of Transportation 

from using such fiscal year 2009 appropriations to promulgate regulations or take any 

action regarding the scheduling of airline operations at any commercial airport in the U.S. 

if such regulation or action involved, among other things, auctioning or rights or 

permission to conduct airline operations, the implementation of peak-period pricing or 

other forms of congestion pricing, withdrawing a right or permission to conduct operations 

at such an airport, or requiring a carrier to transfer involuntarily any such right or 

permission to another. 

and the possible impact of 

the significantly changed economic circumstances on the slot auction 

program, FAA believed it was better to rescind the rule rather than 

propose to extend it. According to DOT’s Office of the Secretary and 

FAA, their Slot and Management Transparency notice of proposed 

rulemaking currently being drafted will propose to replace the current 

temporary orders limiting scheduled operations at JFK, LaGuardia, and 

Newark with a permanent rule to address congestion and delay, while 

also promoting fair access and competition, including establishing a 
 

Page 12 GAO-12-902 Airport Slot Controls

secondary market that would allow airlines to buy and sell slots at the 

New York City area airports.16

In 2009, because airlines are prohibited from selling or purchasing slots 

under the temporary order at LaGuardia, Delta Air Lines and US Airways 

sought a waiver from DOT’s Office of the Secretary and FAA from this 

prohibition to exchange slots at LaGuardia and Reagan National because 

Delta wanted to establish a domestic hub at LaGuardia and US Airways 

wanted to increase service at Reagan National. In 2011, DOT’s Office of 

the Secretary and FAA together granted the joint waiver request that 

permitted the transfer and sale of more than 300 slots between the two 

airlines, provided that they divest a total of 48 slots (24 slot pairs) at 

Reagan National and LaGuardia to new airline entrants and airlines 

holding less than 5 percent of the slots at those airports. After the slot 

swap, Delta Air Lines increased its share of slot holdings at LaGuardia 

from 24 percent in April 2011 to 44 percent in May 2012 and US Airways 

increased its share of slot holdings at Reagan National from 31 percent in 

April 2011 to 54 percent in May 2012. The divestiture effort, conducted 

through a blind sale open to new entrants and limited incumbents only, 

resulted in JetBlue attaining 16 slots at LaGuardia for $32 million and 16 

slots at Reagan National for $40 million, and WestJet attaining 16 slots at 

LaGuardia for $17.6 million. Under the terms of the slot swap, US Airways 

and Delta were to receive the proceeds from the sale of their divested 

slots. 

DOJ is responsible for enforcing antitrust laws for most sectors of the 

economy, including the airline industry. According to DOJ officials, this 

includes reviewing competitive aspects of airlines’ holdings at slotcontrolled airports. For example, transactions that increase concentration 

of slot holdings may substantially lessen competition in violation of the 

antitrust laws. In 2010, DOJ offered formal comments in support of the 

tentative decision by DOT’s Office of the Secretary and FAA to condition 

approval of the slots transfer between Delta Air Lines and US Airways 

with regard to the airlines’ slot holdings at LaGuardia and Reagan 

 

16From 1986 to 2006, when FAA managed congestion at JFK and LaGuardia under the 

High Density Rule, airlines were allowed to buy and sell slots at these airports. However, 

in comments to FAA on a proposed congestion management rule for LaGuardia, some 

airlines indicated that a secondary market did not develop because the Wendell H. Ford 

Aviation Investment and Reform Act for the 21st Century (AIR-21) granted exemptions 

from the High Density Rule’s flight restrictions to some airlines for free.
 

Page 13 GAO-12-902 Airport Slot Controls

National on the airlines divesting a certain number of slots. While DOJ did 

not take action to block the slot swap, DOJ officials told us in June 2012 

that they are still reviewing competitive aspects of the airlines’ slot 

holdings at Reagan National following completion of the revised slot 

swap.

In addition to slot controls, Reagan National and LaGuardia are subject to 

perimeter rules, which limit nonstop flights serving these airports to a 

distance of 1,250 and 1,500 miles,17 respectively. While LaGuardia’s 

perimeter rule is imposed by the airport’s operator, the perimeter rule at 

Reagan National is statutory.18 Two federal laws—the Wendell H. Ford 

Aviation Investment and Reform Act for the 21st Century (AIR-21)19 in 

2000 and the Vision 100-Century of Aviation Reauthorization Act (Vision 

100)20 in 2003—increased the number of slot exemptions at Reagan 

National and for the first time required exemptions to be granted to the 

Reagan National perimeter rule known as “beyond-perimeter” slot 

exemptions. These laws required the Secretary of Transportation to grant 

exemptions to the existing rules, adding 44 slot exemption operations (22 

round trips) per day during a 15-hour period and requiring 24 (12 round 

trips) of these slot exemptions to be granted for beyond-perimeter 

flights.21 In February 2012, the FAA Modernization and Reform Act of 

201222

 

17The perimeter rule for LaGuardia provides an exception for nonstop flights to and from 

Denver because there was existing service to Denver when the rule went into effect.

required the Secretary of Transportation to grant 8 additional 

beyond-perimeter slots exemptions (4 round trips) at Reagan National.

The 2012 act, similar to AIR-21 in 2000 and Vision 100 in 2003, required 

DOT, in awarding the slot exemptions, to consider specified criteria in 

granting beyond-perimeter exemptions. The 2012 act required the 

consideration of issues such as their impact on providing network benefits 

(connecting flights) outside of the perimeter and passenger service to 

small communities. In May 2012, to implement the requirements of the 

18 Pub. L. No. 99-500, 100 Stat. 1783, 1783-375 (1986); Pub. L. No. 99-591, 100 Stat. 

3341, 3341-376 (1986).

19Pub. L. No. 106-181, 114 Stat. 61 (2000).

20Pub. L. No. 108-176, 117 Stat. 2490 (2003).

21The statutes also authorized 20 additional slot exemptions within the 1,250-mile 

perimeter.

22Pub. L. No. 112-95, 126 Stat. 11 (2012). 
 

Page 14 GAO-12-902 Airport Slot Controls

FAA Modernization and Reform Act, DOT awarded the beyond-perimeter 

slot exemptions to airlines proposing to provide nonstop service between 

Reagan National and Austin, Texas; Portland, Oregon; San Francisco, 

California; and San Juan, Puerto Rico. The act also authorized the four 

incumbent carriers at Reagan National to each convert two slots that 

were being used for flights to large hubs within the perimeter, to two slot 

exemptions for nonstop flights beyond the perimeter. Accordingly, four 

round trips were suspended to large hubs and four new round trips were 

initiated instead to Los Angeles, San Diego, and San Francisco, 

California, and Salt Lake City, Utah (using a total of eight slot exemptions) 

(see fig. 2).
 

Page 15 GAO-12-902 Airport Slot Controls

Figure 2: Nonstop Beyond-Perimeter Slot Exemption Destinations from Reagan National from 2000 through 2012
 

Page 16 GAO-12-902 Airport Slot Controls

Appendix III provides more detailed information about the implementation 

of slot controls and perimeter rules, the proposed Slot Management and 

Transparency rule, and the slots transfer between Delta Air Lines and US 

Airways. 

Reagan National has sufficient airside (runway) capacity to accommodate 

the new nonstop beyond-perimeter flights. The airport’s terminal and 

landside facilities are more constrained, but with some improvements and 

adjustments, it will also have sufficient terminal capacity. The new flights 

are also likely to have limited effects on passenger security screening 

wait times, passenger traffic at the other Washington, D.C., area airports, 

MWAA’s ability to service its debt, and aircraft noise. In addition, the low 

cost airlines that will be operating half of the new beyond-perimeter flights 

at Reagan National will increase airline competition on those routes.

Reagan National is routinely operating below the maximum authorized 67 

hourly takeoffs and landings (slots) and the 67.6 hourly takeoffs and 

landings that a 2011 FAA capacity analysis indicated could be 

accommodated based only on average runway capacity.

23 While 67 is the 

maximum number of hourly takeoffs and landings authorized in any one 

hour, the number of slots and slot exemptions authorized on a daily basis 

is generally less than 67 per hour, on average. Table 2 shows the 

maximum number of hourly takeoffs and landings allowed at Reagan 

National, broken down by the type of aircraft operations.

 

23MITRE, an FAA contractor, conducted this analysis in August 2011. For information 

about how MITRE analyzes airport capacity, see Appendix V of GAO, National Airspace 

System: Setting On-Time Performance Targets at Congested Airports Could Help Focus 

FAA’s Actions, GAO-10-542 (Washington, D.C.: May 26, 2010). 

Reagan National Can 

Accommodate New 

Beyond-Perimeter 

Flights, Which Are 

Likely to Have a 

Limited Effect on 

Other Washington, 

D.C., Area Airports

Airside Capacity
 

Page 17 GAO-12-902 Airport Slot Controls

Table 2: Hourly Aircraft Operations (Takeoffs and Landings) Allowed at Reagan 

National

Type of aircraft operations 

Maximum number of takeoffs and 

landings (slots) allowed per hour 

Air carrier 37 a

Commuter aircraft operations 11 b

General aviation and unscheduled flights 12

Slot exemptions 5 c

Slidesd (allowing slots to be used in different time 2 

periods)

Total 67 e

Source: 14 C.F.R. § 93.123, 49 U.S.C. § 41718(c)(2)(A)(ii), 49 U.S.C. § 41714(d)(1) and FAA. 

a

Under FAA slot control regulations applicable to Reagan National, “air carrier slots” are intended for 

operations with turboprop and reciprocating engine aircraft with 75 or more seats or turbojet aircraft 

with 56 or more seats. However, air carrier slots may be used for operations using aircraft of any size. 

FAA officials estimated that 30 to 40 percent of air carrier slots are operated in commuter aircraft slots 

based on a review of published schedules and the number of commuter aircraft operated above the 

commuter slot quota. 

b

Under FAA slot control regulations applicable to Reagan National, “commuter slots” may be used 

only for operations with turboprop and reciprocating engine aircraft with no more than 76 seats or 

turbojet aircraft with fewer than 56 seats. 

c

These are exemptions to the hourly restrictions at Reagan National that are authorized by statute. 

d

Under 49 U.S.C. § 41714 (d)(1), the Secretary of Transportation is authorized to grant certain 

exemptions from specified slot rules applicable to Reagan National. For example, under this authority 

the Secretary may grant exemptions from hourly limitations on slots at Reagan National but may not 

increase the number of aircraft operations in any 1-hour period by more than 2 operations. FAA may 

not grant more than 2 exemptions for a 1-hour period. FAA uses this authority to consider requests 

for what are referred to as a grant “slot-slides,” which would allow slots allocated for certain hours to 

be reassigned and used in a different slot periods. 

e

Our analysis of FAA data found that a maximum of about 53 slots was 

allocated and used per hour at Reagan National, compared with the 67 

hourly takeoffs and landings that are generally permitted. Specifically, 

FAA reported that a maximum of 52 slots in one hour was allocated for 

airline and commuter operations in April 2012 and an average of about 1 

aircraft operation per hour was used for general aviation or unscheduled 

Regulatory limits are 60 per hour. However, slot exemptions are authorized by statute to increase 

hourly operations by up to 5 in an hour, but only between 7:00 a.m. and 9:59 p.m. In addition, slot 

slides may also increase operations but under statute (1) may not result in an increase in the total 

number of slots per day, (2) may not result in an increase in the total number of slots from 7:00 a.m. 

to 9:00 p.m., and (3) may not increase operations in any 1-hour period by more than two operations. 

FAA has not modeled the delay impact of 67 operations in each hour. 
 

Page 18 GAO-12-902 Airport Slot Controls

aircraft operations from May through August 2011.24 The new beyondperimeter flights will cause the largest increase in the maximum number 

of slot allocations for airline and commuter aircraft operations from 4:00 

p.m. to 6:59 p.m., when the number of slot allocations will increase by 2 

per hour.25

Table 3: Impact of New Beyond-Perimeter Exemptions on Average Peak and Non-Peak Hour Slot Allocations at Reagan 

National for the Summer 2012 Season

Table 3 shows the impact of the new beyond-perimeter flights 

on slot allocations during peak and nonpeak hours. 

Type of aircraft 

operations 

Average number of 

slots allocated per hour 

during peak hoursa

Average number of 

slots allocated per hour 

during peak hoursa

including the new 

beyond-perimeter 

flights

Average number of 

slots allocated per 

hour during nonpeak 

hours b

Average number of slots 

allocated per hour during 

nonpeak hours including 

the new beyond-perimeter 

flights

Airline and commuter 

operations

b

51.3 c 52.5 45.6 45.7

Source: GAO analysis of FAA data.

a

Peak hours used in this analysis are from 7:00 a.m. to 10:00 a.m. and from 4:00 p.m. to 7:00 p.m. 

b

New beyond-perimeter slots that Congress authorized in February 2012. 

c

Based on FAA data regarding slot holders for Thursdays for the summer 2012 season as of April 5, 

2012. 

Much of the difference between the maximum number of hourly aircraft 

operations authorized and the average number of slots allocated and 

used can be attributed to a substantial decrease in general aviation and 

unscheduled aircraft operations at Reagan National after the September 

11, 2001, terrorist attacks. After the 2001 terrorist attacks, TSA imposed 

security restrictions on general aviation operations operating at Reagan 

National, such as requiring an armed security officer to be on board all 

 

24Based on an FAA analysis of unscheduled operations from May through August 2011 

indicating that there was an average of 17.3 daily general aviation operations weekdays 

from 6:00 a.m. to 10:59 p.m. We reported in 2007 that there were about 200 general 

aviation and unscheduled flights at Reagan National in 2006, or an average of one-half of 

a flight operation per day. The number of general aviation and unscheduled flights has 

increased at Reagan National since 2006 in part because TSA updated security 

procedures that made more general aviation flights possible, for example, by expanding 

the number of airports from which flights can emanate.

25From 4 p.m. to 4:59 p.m., the number of slot allocations will increase from 52 to 54, and 

from 5 p.m. to 5:59 p.m. and from 6 p.m. to 6:59 p.m., the number of slot allocations will 

increase from 51 to 53. 
 

Page 19 GAO-12-902 Airport Slot Controls

flights. Before the attacks, there were about 210 general aviation and 

unscheduled flights per day at Reagan National. By comparison, FAA 

indicated that there were about 17 general aviation and unscheduled 

flights per day at Reagan National in 2011.26 Of the 60 authorized hourly 

slots at Reagan National, excluding any slot exemptions, 12 are allocated 

for general aviation aircraft operations or other aircraft that do not operate 

on a scheduled basis. However, from May through August 2011, an 

average of about 1 of the 12 allocated slots was used per hour. Although 

airlines with large commercial aircraft could not necessarily use the slots 

reserved for smaller general aviation aircraft and unscheduled flights, 

which may use the airport’s shorter runways and do not generally use 

airport gates and terminal infrastructure, the reduced amount of overall 

general aviation traffic leaves some airport capacity unused. In addition, 

some slots are available at Reagan National during nonpeak hours 

because airlines are primarily interested in obtaining slots at peak hours.

FAA indicated that, for July and August 2012, 34 airline and 12 commuter 

slots were available, all at early morning (6:00 a.m.) or late evening 

(10:00 p.m. or 11:00 p.m.) hours.27

Although Reagan National has sufficient airside capacity to accommodate 

the new beyond-perimeter flights, the airport has more limited terminal 

capacity, which includes space for gates, ticket counters, baggage 

handling, and security screening. As of May 2012, two of the new 

beyond-perimeter round trips (those operated by Jet Blue and Southwest 

Airlines) are expected to be operated out of Terminal A, the airport’s 

original terminal that opened in 1941, and two of the new beyondperimeter round trips (those operated by Virgin America, which is the 

airport’s only new airline entrant among the operators of the new beyondperimeter flights, and Alaska Airlines) are expected to be operated out of 

the newer Terminal B/C, which opened in 1997. To help accommodate as 

many as 1,245 additional daily passengers who could fly on the new 

beyond-perimeter flights, MWAA is planning to expand baggage and 

 

26Based on an FAA analysis of general aviation and unscheduled weekday operations 

from May through August 2011. 

27Three slots each were available at 6:00 a.m. and 10:00 p.m. and 40 were available at 

11:00 p.m. These numbers exclude other slots that are allocated on an ad hoc day-of 

basis following a request from the operator and one commuter slot that is available at 9:00 

p.m. and another at 10:00 p.m. that are allocated on a temporary basis and subject to 

recall by FAA.

Terminal Capacity
 

Page 20 GAO-12-902 Airport Slot Controls

security screening space in Terminal A and complete those 

improvements by the summer of 2013. An MWAA official said these 

improvements were already needed to address increased passenger 

volume and complexity of operations in Terminal A. For example, seven 

airlines, each with its own needs for space in Terminal A,28 are now 

operating separate, uncoordinated schedules, compared with a few years 

ago when one dominant airline and a few smaller airlines were operating 

there. No improvements will be needed to accommodate the new beyondperimeter flights in Terminal B/C. MWAA estimated that improvements in 

Terminal A will cost about $45.6 million, which will be financed through 

bond funds and airline leases. However, an MWAA official added that 

these improvements do not allow for any additional growth in Terminal A, 

which could, if needed, require replacing the terminal at a cost of several 

hundred million dollars.

Based on current gate usage rates at Reagan National, on average, 

gates will be fully used. MWAA data indicated that airlines operating at 

Reagan National will average 7.7 turns per day for each gate. This is in 

the range of six to eight daily turns per gate that was defined as full gate 

utilization in a 2010 Transportation Research Board study29 on commonuse gates. That report also indicated that full gate utilization may be 

affected by noise restrictions limiting the hours of operations or other 

factors that may vary according to the airline using the gate. Exceeding 

full gate utilization could lead to flight delays.

We asked TSA to estimate the impact of the new beyond-perimeter flights 

on passenger security screening wait times at Reagan National using the 

agency’s security screening throughput model. TSA’s model suggested 

that the impact of the new beyond-perimeter flights on passenger security 

 

28The official said that although these airlines need the same type of space to function, 

e.g., ticket counters, gates, and baggage systems, each airline needs a different amount 

of space, so economies of scale cannot always be maximized.

29Transportation Research Board of the National Academies, Reference Guide on 

Understanding Common Use at Airports, (Washington, D.C.: 2010).

Gate Usage

Passenger Security 

Screening
 

Page 21 GAO-12-902 Airport Slot Controls

screening wait times would be minimal.30

The additional beyond-perimeter flights are not expected to affect access 

to the airport or parking, considering that the maximum number of 

additional passengers that the new flights could generate represents 

about 5 percent of the airport’s total daily enplanements. According to a 

survey of air passengers in the Washington, D.C., and Baltimore area, 16 

percent of Reagan National passengers arrive by Metrorail, which is 

among the highest public transportation rates in the nation for airport 

access, 74 percent of passengers arrive by car (private and rental) or taxi, 

and the remaining 10 percent arrive by shuttle bus or Metrobus.

However, an MWAA official said 

that until improvements to the security screening space in Terminal A are 

completed next summer, passengers may need to wait longer to be 

screened at that checkpoint.

31

 

30We asked TSA to assess the impact of the new beyond-perimeter flights on wait times 

using its security screening throughput model. As inputs to the model, we provided TSA 

with the flight times for the new beyond-perimeter flights, data on the maximum number of 

passengers on those flights, and the screening checkpoints that the passengers would 

use. Although the results from this model suggested that any increase in wait times at 

Reagan National would be minimal, we are not reporting the precise estimates of wait time 

changes because they would imply a greater level of precision than the model could 

reasonably provide.

MWAA 

provided data showing that since parking facilities were expanded since 

2009, the number of times that lots have been filled to capacity has 

dropped considerably. The data indicated that in 2011, the airport’s 

parking lots were filled to capacity approximately 38 times, compared with 

2009, when they were filled to capacity a total of 353 times. According to 

MWAA, from January through May 2012, the parking lots were filled to 

capacity 13 times. However, an MWAA official said that the impact of the 

new beyond-perimeter slot exemptions should not be considered in 

isolation and that the sale of slots to JetBlue under the Delta-US Airways 

slots swap earlier in 2011 has had a more pronounced effect. For 

example, the official said that since more JetBlue flights began operating 

out of Terminal A in June 2012, the economy parking lot has been filled to 

capacity an average of 4 days a week. In providing comments on a draft 

of this report, MWAA indicated that during the first 8 months of 2012, the 

economy parking lot has been filled to capacity more than 60 times, which 

31National Capital Region Transportation Planning Board and Metropolitan Washington 

Council of Governments, Draft 2011 Washington-Baltimore Regional Air Passenger 

Survey, (Washington, D.C.: May 2011). 

Airport Access and 

Parking
 

Page 22 GAO-12-902 Airport Slot Controls

was more than double the number of times that the lot was forced to 

close in 2011.

Our analysis found that the beyond-perimeter flights authorized in 

February 2012 could add between zero (assuming that no new 

passengers shift from using other airports) and a maximum of 1,245 daily 

enplanements (departing passengers) at Reagan National.32

Longstanding policy designed to guide the operation of Reagan National 

and Dulles, as well as agency rules designed to implement such policy, 

have included the roles of Reagan National in providing short-haul 

domestic service and Dulles in providing all types of service.33

 

32In calculating the maximum number of enplanements, we included the eight new daily 

beyond-perimeter departures and assumed that each daily flight used the aircraft specified 

in the airline’s application for the slot exemption and that those aircraft were 100 percent 

full. We did not include the passenger impact of the within-perimeter flights that were 

converted to beyond-perimeter slot exemptions because there were too many unknown 

factors, such as whether the passengers on those flights were connecting or originating at 

Reagan National or the load factors on them. 

In addition, 

under the policy, MWAA is to promote the “better utilization” of Dulles, 

which was underutilized for many years after opening in 1962. During our 

review, MWAA and BWI officials expressed concern about the possible 

impact of the new beyond-perimeter flights at Reagan National on 

passenger traffic at Dulles and BWI. We found, on the basis of 2011 

enplanement data, that if all of the new beyond-perimeter flights are 100 

percent full, the number of enplanements on those flights would represent 

an increase of about 5 percent of annual enplanements at Reagan 

National. Correspondingly, Dulles or BWI would lose a maximum of 4.1 

percent of their enplanements, respectively, if all the passengers changed 

from using either of these two airports to using Reagan National. 

Therefore, if all the passengers changed from using Dulles or BWI, the 

new beyond-perimeter flights are likely to have some impact on 

passenger traffic at these airports. However, it is extremely unlikely that 

33In 1981, FAA adopted rules to implement FAA’s Metropolitan Washington Airports’ 

policy (45 Fed. Reg. 62398 (Sept. 18, 1980)) to guide the future operations and 

development of Reagan National and Dulles. This implementing Metropolitan Washington 

Airport rule provided, among other things, that the perimeter rule would maintain the longhaul nonstop service at Dulles and be consistent with the roles proposed for Reagan 

National as a short/medium-haul facility and for Dulles as an unrestricted facility available 

for all types of operations. 48 Fed. Reg. 58036 (Nov. 27, 1981). In 1986, the federal law 

creating MWAA provided that the regulations of MWAA’s predecessor agency shall 

become the regulations of MWAA. Pub. L. No. 99-500, 100 Stat. 1783, 1783-375 (1986); 

Pub. L. No. 99-591, 100 Stat. 3341, 3341-376 (1986).

Impact on Other Airports 

in the Washington, D.C., 

Area
 

Page 23 GAO-12-902 Airport Slot Controls

all of these passengers would shift from using one airport; instead, any 

loss likely would be shared between Dulles and BWI. In addition, the 

airports are not perfect substitutes for Reagan National, so it is unlikely 

that all the passenger traffic would shift from Dulles or BWI. But, even in 

the worst case, a 4.1 percent change is less than the growth expected at 

these airports over the next 2 or 3 years. The actual impact of the new 

beyond-perimeter flights at Reagan National on passenger traffic at the 

other Washington, D.C., area airports cannot be quantified because all of 

the new flights did not start until August 2012 and because of unknown 

factors such as how competing flights will be priced, how the new direct 

flights at Reagan National will draw passengers from the area airports, 

how other airlines may adjust their schedules, and the extent to which the 

new flights may generate new passenger demand on those routes.

We found no evidence that the previously added beyond-perimeter flights 

at Reagan National had affected passenger traffic or airfares at the 

surrounding airports. We found two cases—one in 2005 and another in 

201234—when airlines discontinued or planned to discontinue service 

between Dulles and beyond-perimeter destinations after they were 

awarded new beyond-perimeter slot exemptions at Reagan National, but 

any shift in passenger traffic, as noted above, represented about 4 

percent of overall passenger traffic. (Figures 8 through 31 in appendix IV 

show trends in average annual passenger traffic and airfares at BWI and 

Dulles for destinations granted beyond-perimeter slot exemptions at 

Reagan National under AIR-21 and Vision 100 between 2000 and 2004).

Moreover, any deviation in airfares after the initiation of the slot 

exemptions at Reagan National could be a result of many factors, such as 

airline bankruptcies and mergers. Additionally, the presence of low cost 

airlines on the newly-awarded beyond-perimeter flights will increase 

competition on those routes and could help reduce airfares to those 

destinations. However, of the four new nonstop beyond-perimeter 

destinations, only one low cost airline (Virgin America) will be competing 

with a legacy airline (United Airlines) in providing service between 

Reagan National and San Francisco.

 

34The 2005 example involved Frontier Airlines and the 2012 example involved Delta Air 

Lines.
 

Page 24 GAO-12-902 Airport Slot Controls

If the new beyond-perimeter flights cause passengers to shift from using 

Dulles to using Reagan National, it could increase per passenger airline 

costs of using Dulles, which, if substantial, could cause the airlines to 

reduce service at the airport. To better understand the potential financial 

impact of possible changes in passenger traffic resulting from the new 

beyond-perimeter exemptions, we asked MWAA to estimate the flights’ 

impact on the cost per enplaned passenger,35 which is a generalized 

measure of airline’s airport charges, assuming a worst case scenario.

Assuming all of the passengers on the new beyond-perimeter flights 

shifted from using Dulles to using Reagan National—the worst case 

scenario—and all other factors stayed the same, MWAA’s analysis found 

that the cost per enplaned passenger would increase at Dulles in 2013 by 

$1.10, or 3.9 percent, and increase in 2014 by $1.51 or 5.7 percent, and 

decrease at Reagan National in 2013 by $0.58, or 4.4 percent, and 

decrease in 2014 by $0.89, or 6.5 percent (see table 4). These results 

show that because the same costs, most of which are fixed costs, would 

be spread among fewer passengers at Dulles and more at Reagan 

National so that the cost per enplaned passenger would change 

accordingly. However, even in the worst case, the changes would be 

relatively small.

 

35Cost per enplaned passenger is defined as all landing fees, airside usage charges, fuel 

flowage fees, terminal rents, and other terminal payments to an airport, divided by the 

number of enplaned passengers. We did not assess the possible impact of the new 

beyond-perimeter flights on the cost per enplaned passenger at BWI because of 

differences in how airport authorities calculate those numbers. Airlines use cost per 

enplaned passenger as a standardized measure of relative unit costs to compare costs 

among airports.

Financial Impact on 

MWAA
 

Page 25 GAO-12-902 Airport Slot Controls

Table 4: Projected Impact of the New Beyond-Perimeter Flights at Reagan National on the Cost per Enplaned Passenger in 

2013 and 2014

Airport

Projected 2013 cost per 

enplaned passenger

Projected 2013 cost per 

enplaned passenger with 

new beyond-perimeter 

flights 

Projected 2014 cost per 

enplaned passenger

Projected 2014 cost per 

enplaned passenger with 

new beyond-perimeter 

flights 

Reagan National $13.23 $12.65 a $13.70 $12.81 b

Dulles $27.99 $29.09 c $26.61 $28.12 d

Source: MWAA

a

Based on projected enplanements of 9,765,000. 

b

Based on projected enplanements of 9,850,000. 

c

Based on projected enplanements of 12,095,000. 

d

Based on projected enplanements of 12,415,000. 

In recent years, the cost per enplaned passenger has increased 

substantially at Dulles, owing to a major capital development project at 

the airport, while it has decreased slightly at Reagan National. From 2010 

to the first half of 2012, the cost per enplaned passenger at Dulles 

increased from $17.16 to $26.03 or 51.7 percent, but decreased at 

Reagan National from $12.84 to $12.74, or 0.8 percent. Airline 

representatives generally told us that an airport’s cost as measured by 

cost per enplaned passenger is among many factors that they consider 

when deciding whether to provide service there. However, 

representatives from one large airline said that if the cost per enplaned 

passenger at Dulles and other costs such as fuel continue to increase, it 

would consider reducing or cancelling its service there. MWAA officials 

also said that, given the recent substantial increases in the cost per 

enplaned passenger at Dulles, some airlines may stop serving the airport, 

particularly in providing domestic service, and that an increase of even 

one dollar in the cost per enplaned passenger is significant.36

 

36For comparison purposes, MWAA provided data showing that the costs per enplaned 

passenger was substantially higher at Dulles than at most other large hub airports.

However, these data were not directly comparable because airports vary in terms of what 

airlines and airports pay for, which affects the costs per enplanement.

In a recent 

credit-rating report on MWAA prepared in September 2011, before the 

new beyond-perimeter flights were awarded, one agency had a negative 

outlook on the authority’s rating because of expected significant increases 

in the cost per enplaned passenger and lower debt service coverage over 

the next 5 years. However, two other credit-rating agencies reported in 
 

Page 26 GAO-12-902 Airport Slot Controls

September 2011 their ratings outlooks for MWAA were stable, citing the 

strong air passenger market in the Washington, D.C., area. Moreover, 

recent increases in the cost per enplaned passenger at Dulles were not 

due to significant shifts in passenger traffic. From 2010 through 2011, 

enplanements at Dulles decreased by about 2 percent, while they 

increased at Reagan National by about 3.6 percent. However, from 2010 

and 2011, international enplanements—which generate higher airport 

revenues because airline fees are based in part on aircraft weight, and 

aircraft used for international flights are generally larger and heavier—

increased at Dulles by more than 4 percent and represented 28 percent 

of all enplanements in 2011. In addition, in a forecast of airport activity 

from 2011 to 2040, FAA ranked Dulles second among 30 major U.S. 

airports in terms of projected increases in enplanements, with a projected 

annual growth rate of 3.9 percent. FAA projected that from 2011 to 2040, 

enplanements at Dulles will increase by 215 percent, compared with 34 

percent at Reagan National and 110 percent at BWI.37

Under current lease agreements between MWAA and its incumbent 

airlines, debt costs are not shared between the two airports which could 

make servicing the much larger debt at Dulles difficult if revenue declines 

at Dulles were substantial. MWAA currently maintains $5.2 billion in longterm debt.38 Much of MWAA’s debt was incurred for recent major capital 

improvements at Dulles, such as an automated train system39 connecting 

the main terminal to gates and construction of a fourth runway. According 

to an MWAA official, about $3.8 billion of the $5.2 billion in total debt is 

allocated to Dulles and about $1.4 billion is allocated to Reagan 

National.40

 

37Federal Aviation Administration, Terminal Area Forecast Summary, Fiscal Years 2011-

2040.

MWAA officials are concerned about the financial impact of 

the new beyond-perimeter flights on the authority’s ability to service its 

38According to Moody’s Investors Service, Inc., MWAA is among five U.S. airport 

authorities with the most debt. In 2011, MWAA incurred $222 million in interest expense.

39The automated passenger train system at Dulles, called Aerotrain, is separate from the 

project to extend Metrorail to Dulles. MWAA aviation funds are responsible for 4.1 percent 

of the total cost of the Metrorail extension to Dulles. However, according to MWAA, all 

bonds for the corridor project are backed by a separate MWAA toll road credit that is 

firewalled from the MWAA’s aviation credit. 

40According to an MWAA official, debt is not issued on an airport-by-airport basis; but 

rather as airport-system revenue-bond debt for both airports. However, MWAA tracks 

where the debt proceeds are applied by airport. 
 

Page 27 GAO-12-902 Airport Slot Controls

debt at Dulles, because revenues and debt service charges for Reagan 

National and Dulles are maintained separately.41

With respect to MWAA’s authority to generate additional revenues that 

could help mitigate the cost per enplaned passenger in the future, the 

FAA Modernization and Reform Act of 2012 amended the definition of the 

“airport purposes” that MWAA may engage in to include “a business or 

activity not inconsistent with the needs of aviation that has been approved 

by the Secretary.”

According to MWAA 

officials, in the event that one of the two airports could not pay its debt, 

the lease agreements contain an “extraordinary coverage protection 

payments” provision designed to allow for the sharing of debt service 

between the two airports. More specifically, according to MWAA officials, 

if Dulles could not continue paying its debt service, the use of the 

extraordinary coverage provision by the authority could have the impact 

of mitigating airline rates and charges at Dulles and, in turn, could 

mitigate a cost per enplaned passenger increase at Dulles and cause a 

corresponding increase in the cost per enplaned passenger at Reagan 

National. However, an MWAA official said that the airports authority does 

not expect that this provision will be triggered before the current lease 

agreements expire in the fall of 2014. In addition, the MWAA official said 

the inclusion of this provision in the new leases is a matter that will be 

negotiated with the airlines.

42 An MWAA official said that, pursuant to this authority, 

the airport authority plans to develop land near Dulles for warehouses, 

cargo-related integrators, freight forwarders, and general aviation.

However, the official added that the property first needs to undergo an 

environmental impact review, which could take 2 to 3 years, and that new 

revenues from the development are not expected to have an impact on 

airline lease rates in the next 3 to 7 years.

Although some members of the community surrounding Reagan National 

expressed limited concerns about the additional aircraft noise that the 

new beyond-perimeter flights could generate, FAA and airport officials 

 

41MWAA receives revenues from landing fees, which are based on aircraft weight; airport 

leases with airlines; and concessions. Although non-aeronautical revenues, such as 

concessions, are not maintained separately by airport, MWAA officials said revenues are 

not sufficient to cover much debt.

42Pub. L. No. 112-95, 126 Stat. 11, 92 (2012).

Aircraft Noise
 

Page 28 GAO-12-902 Airport Slot Controls

indicated that the relatively small number of flights being added will not 

have a significant overall effect on aircraft noise. Concerns about noise 

affecting nearby residential areas were a primary reason why Reagan 

National became subject to the perimeter rule in the 1960s, when aircraft 

were noisier than they are today. We interviewed individuals from 

community organizations concerned about aircraft noise at Reagan 

National as well as officials from the Washington Council of 

Governments, the Arlington County (Va.) Council, MWAA, and FAA about 

the possible impact on aircraft noise from the new beyond-perimeter 

flights. Individuals from community organizations said they were 

concerned about aircraft noise at the airport as a whole and that 

continuing to add more beyond-perimeter flights has a cumulative 

negative effect. The Washington Council of Governments opposed 

changing the slot or perimeter rules at Reagan National, which the 

organization indicated are important tools in helping to manage the 

volume of air traffic at the airport and the impact on aircraft noise on the 

surrounding community. In addition, the Arlington County Council official 

said that people would notice noise from the new flights if they were 

added in the early morning or late evening hours. However, MWAA and 

FAA officials said that the additional beyond-perimeter flights are not 

expected to cause a noticeable increase in aircraft noise because they 

constitute only 8 of about 800 daily flights at Reagan National, or about 1 

percent, of the total daily aircraft operations. They also noted that aircraft 

make less noise than they did in the past and that the types of aircraft 

being used or planned to be used for the new beyond-perimeter flights 

(Airbus 319s and 320s and Boeing 737s) tend to be newer and quieter. 

An MWAA noise abatement official also said and that in February 2012, a 

new advanced navigational procedure was implemented for northbound 

departures at Reagan National, which is designed for aircraft to follow the 

river and fly less directly over homes. FAA and MWAA officials also said 

that because of the technological advances, noise contours, which 

highlight areas of significant aircraft noise exposure surrounding the 

airport, have generally shrunk and that while noise from the new beyondperimeter flights would be noticeable individually, the relatively small 

number of new beyond-perimeter flights being added as a whole is not 

significant enough to require updating the airport’s noise compatibility 

study.43

 

43FAA supports airports’ efforts to mitigate aviation noise mainly through its voluntary 

noise compatibility program, known as the Part 150 Noise Compatibility Program, which 
 

Page 29 GAO-12-902 Airport Slot Controls

MWAA, which monitors noise at Reagan National, provided data showing 

that in 2011, it received 505 complaints from 117 callers, 255 of which 

came from 5 callers, compared with 197 complaints in 2010 and 99 

complaints in 2009. An MWAA official attributed the increased number of 

complaints to construction on the main runway last year, which is now 

complete. During construction, pilots took a different flight path over 

residential areas at night, rather than following the normal path along the 

Potomac River.

Even though the New York City area airports still experience some of the

worst delays in the country, the delay situation at these airports would be 

far worse in the absence of slot controls.44 The best example of what 

would occur without slot controls at New York City area airports occurred 

in 2000 when a then-new federal law required the Secretary of 

Transportation to grant exemptions to the High Density Rule at JFK and 

LaGuardia to new entrant airlines and for service to small communities 

with small regional jets.45

 

provides guidance to airports on how to develop noise compatibility plans to mitigate noise 

on and around airports. MWAA last conducted a noise compatibility study on Reagan 

National in 2004. See also the forthcoming GAO report, Airport Noise Grants: FAA Needs 

to Better Ensure Project Eligibility and Improve Strategic Goal and Performance 

Measures, 

Soon after, qualifying airlines requested more 

GAO-12-890. 

44Slot controls are one type of demand management measure used to help manage 

congestion. Other demand management measures include congestion pricing and slot 

auctions.

45Wendell H. Ford Aviation Investment and Reform Act for the 21st Century (AIR-21), Pub. 

L. No. 106-181 (2000). AIR-21 mandated that the High Density Rule slot controls would no 

longer apply to JFK and LaGuardia after January 2007. The exemptions for new entrant 

airlines and for service to small communities using regional jets at JFK and LaGuardia 

were interim measures until the AIR-21 slot related phase-out became effective. 

Slot Control Rules 

Help Manage 

Congestion, but 

Allowing Airlines Not 

to Use Some Slots 

May Hinder 

Competition

Slot Control Rules Help 

FAA Manage Congestion
 

Page 30 GAO-12-902 Airport Slot Controls

than 600 new slot exemptions at LaGuardia and by September 2000, 25 

percent of the flight delays in the United States were attributed to 

congestion at LaGuardia. FAA reports that after it again capped the 

number of scheduled takeoffs and landings at LaGuardia in 2001, aircraft 

delays of 15 minutes or more fell from 330 per day in October 2000 to 98 

per day in April 2001.46 In setting operating limits at JFK and Newark in 

2008, FAA conducted analyses with the goal of reducing average 

departure delays at JFK by about 15 percent compared with their 2007 

level, and to keep delays at Newark from increasing above their 2007 

level.47 Airline representatives with whom we spoke mostly agreed that 

some form of slot controls are needed at the four airports to manage 

congestion. However, representatives from two airlines believed that if 

slot controls were lifted, congestion initially would spike, but airlines would 

eventually make the adjustments needed to reach a level of manageable 

congestion.

Existing slot control rules require airlines to operate their slots at least 80 

percent of the time, which allows airlines to not schedule some of their 

allocated slots. FAA has interpreted the rules to allow airlines to apply the 

usage requirement across a pool of slots they hold within a slot period—

an allowance that provides an advantage to airlines with large slot 

holdings in meeting the usage requirement. Further, FAA’s current 

process for overseeing airlines’ compliance of the 80 percent slot usage 

requirement, including its recordkeeping, does not provide sufficient 

assurance that it can adequately identify instances when airlines do not 

meet the 80 percent slot usage requirement. We also found that airlines 

tend to underutilize the slots they do operate at slot-controlled airports as 

 

46In announcing its intent to limit the number of slot exemptions allowed to operate at 

LaGuardia, FAA noted language in section 231 of AIR-21 providing, in general, that AIR21’s slot phase out provisions shall not be construed to affect FAA’s authority for safety 

and the movement of air traffic. 65 Fed. Reg. 69126 (Nov. 15, 2000). FAA explained that

under its authority for safety and the movement of air traffic, and pending the development 

of a longer term solution, it sought to temporarily cap AIR-21 slot exemptions at 

LaGuardia. This limit, according to FAA, still allowed a significant increase in operations at 

the airport above the regulatory limits, thus serving congressional objectives while 

stretching capacity to its practical limits. 71 Fed. Reg. 51360 (Aug. 29, 2006).

47FAA and its federally funded research and development center, the MITRE 

Corporation’s Center for Advanced Aviation System Development, used a model that 

estimated the level of delay associated with various levels of operations at both JFK and 

Newark airports. 

Despite Demand for 

Additional Slots at SlotControlled Airports, Some 

Slots Go Unused While 

Others Are Underutilized
 

Page 31 GAO-12-902 Airport Slot Controls

compared with like-sized airports that are not slot-controlled.48

Specifically, flights operated at slot-controlled airports tend to use smaller 

aircraft and are on average less full, which means that fewer passengers 

are served then would be otherwise.

Available airport capacity at slot controlled airports can go unused in 

three distinct ways. The first of these are slots that are unallocated (i.e., 

slots that are not currently held by any airline). These slots, however, are 

generally at times of day that airlines find undesirable, such as early 

morning or late evening slots. Although unallocated slots go unused, they 

are available for any airline to request and operate.49 Second, some 

additional amount of available capacity goes unused because airlines do 

not schedule all of the slots that they are allocated. Third, more capacity 

goes unused because airlines do not operate all of the flights that they 

schedule, although this is in part because of cancellations resulting from 

unforeseeable circumstances.50 As discussed below, we could not 

calculate precisely how much capacity is unused among these three 

levels or even overall because current airline reporting and FAA 

recordkeeping do not allow these calculations. Figure 3 illustrates the 

three areas in which capacity can go unused at slot-controlled airports. 

The amount that goes unused varies depending on the airport, airline, 

time of year, and demand for air travel.

 

48Because our analysis did not assess the behavior of individual airlines, we could not 

determine the prevalence of this practice among airlines. See appendix V for a detailed 

discussion of our analysis and the results.

49FAA officials told us that some additional operations have been added in less desirable 

hours.

50According to DOT and enforcement case precedent, airlines may not routinely cancel 

flights for economic reasons. This practice, according to DOT, would constitute an unfair 

method of competition to engage in “unrealistic scheduling of flights” identified in 14 

C.F.R. § 399.81 as an unfair or deceptive practice. See, DOT Order 97-1-6, Bellair 

Incorporated (Jan. 13, 1997).

Unused Capacity
 

Page 32 GAO-12-902 Airport Slot Controls

Figure 3: Areas of Unused Capacity at Slot-Controlled Airports

Although slot control rules require airlines to operate their slots at least 80 

percent of the time, or the slots are subject to withdrawal by FAA, the 

rules do not require a minimum level for which the airlines must schedule 

their slots. Therefore, the usage requirement allows airlines to not 

schedule or to suspend flights for operational reasons (such as 

cancellations because of bad weather or ground delays) up to 20 percent 

of the time.51

 

51Under specified circumstances, FAA may waive the 80 percent usage requirement. For 

example, with respect to JFK, LaGuardia, and Newark, FAA may waive the usage 

requirement “in the event of a highly unusual and unpredictable condition which is beyond 

the control of the carrier and which affects carrier operations for a period of five 

consecutive days or more.” Waiver provisions applicable to Reagan National require such 

a condition to exist for a period of 9 or more days. 76 Fed. Reg. 18616 (Apr. 4, 2011); 76 

Fed. Reg. 18618 (Apr. 4, 2011); 76 Fed. Reg. 18620 (Apr. 4, 2011); 14 C.F.R. § 93.227.

According to FAA officials, it is not the agency’s intention for 

airlines to operate at the minimum usage rate of 80 percent because 

unforeseen circumstances would result in the airline losing their slots. 

Unscheduled Slots
 

Page 33 GAO-12-902 Airport Slot Controls

Generally, airlines consider slots that they hold to be valuable assets, in 

part, because slots are a scarce resource that allows airlines to operate 

flights at airports with a high demand for air travel.52 However, airlines 

may not need all of their allocated slots at a point in time. Even so, 

airlines still have an incentive to hold onto their slots, even if that means 

leasing them, because if they return them to FAA the slots could be 

reallocated to a competitor. During our review, we found that airlines at 

U.S. slot-controlled airports are not scheduling all of their allocated slots. 

Specifically, our analysis of aggregated airline schedules for certain days 

in 2011, indicated that generally airlines in aggregate scheduled between 

80 percent and 100 percent of their slot allocations (depending on the 

airport, day of week, and season), but on specific days, one or more 

airlines scheduled as little as 75 percent of all daily allocated slots.53

Internationally, where slot controls are more prevalent than in the United 

States, airlines generally schedule all of their slots. IATA representatives 

told us that airlines operating at slot-controlled airports outside of the 

United States generally schedule 100 percent of their allocated slots and 

that it may be seen as abuse if they don’t schedule all of their slots. Under 

the Worldwide Slot Guidelines, airlines may only hold slots that they 

intend to operate, transfer, exchange or use in a shared operation, and 

violations are subject to sanction under local regulation or national law. 

FAA, however, in implementing U.S. slot control rules, generally does not 

calculate or know airlines’ schedule rates. Requiring airlines to schedule 

all of their slots could encourage airlines to sell or lease slots to airlines 

that desire them or return slots to FAA that they do not intend to use, but 

it could also cause airlines to operate more flights than necessary to meet 

demand for routes within their business model as a means of meeting the 

80 percent usage requirement. Airlines would only operate additional 

Because slot usage is measured across multiple days of a reporting 

period—all days within a 2-month period at Reagan National and 

LaGuardia and each day of the week within a season for JFK and 

Newark—airlines can schedule less than 80 percent of their allocated 

slots on a single day and still meet the 80 percent usage requirement.

 

52Although airlines might consider slots to be valuable assets, FAA slot regulations at 14 

C.F.R. § 93.223(a), for example, provide that slots do not represent a property right but 

represent an operating privilege subject to absolute FAA control.

53To conduct this analysis, we compared the total number of scheduled flights for each of 

7 days in February 2011 and each of 7 days in August 2011 with daily slot allocation 

numbers provided by FAA for each slot-controlled airport.
 

Page 34 GAO-12-902 Airport Slot Controls

flights, though, if the perceived cost of relinquishing their slot—such as 

the risk of a competitor operating the slot—is higher than the cost they 

would incur from operating the flight.

FAA’s current process for overseeing airlines’ compliance of the 80 

percent slot usage requirement, including its recordkeeping, does not 

provide sufficient assurance that it can adequately identify instances 

when airlines do not meet the 80 percent slot usage requirement. FAA 

uses a slot management system to compile usage data reported by 

airlines and validate that data against FAA’s slot allocation records. FAA 

then reviews instances of potential noncompliance on an exception 

basis—that is, FAA reviews only those instances that its system identifies 

as below the 80 percent slot usage rate. Our review of FAA’s process for 

overseeing airlines’ slot usage, combined with FAA’s inability to provide 

documentation verifying airlines’ compliance with the usage requirement 

and our limited analysis of FAA aggregated data on airlines’ flight 

schedules and slot allocation records, raised questions regarding FAA’s 

ability to effectively identify instances of noncompliance. Issues we 

identified include the following.

• Usage rates are generally not calculated: At the end of each reporting 

period, airlines submit reports to FAA that include the minimum 

required data for each slot, including whether the slot was operated, 

the flight number, and the scheduled time of departure, but do not 

include actual usage rates. FAA officials said that they do not 

calculate the actual slot usage rate for each airline’s slot holdings, in 

part, because the format in which airlines report the data makes it 

difficult to correlate the slots to the flights that were operated. For 

example, flights operated by Airline A using slots leased or exchanged 

from Airline B may be reported by Airline A, but would need to be 

considered in Airline B’s usage rate but not in Airline A’s rate. The 

airline reports generally do not make this distinction. Furthermore, 

FAA does not require airlines to report the same flight in a specific slot 

throughout the reporting period, which further complicates FAA’s 

ability to correlate a slot to the flight that was operated. Without 

calculating airlines’ actual usage rate, FAA does not know precisely 

how much available capacity goes unused, which hinders its ability to 

manage slots and the airspace.

• Reliance on self-reported data in a variety of formats: Instead of 

calculating the actual usage rate, FAA compares airlines’ reported 

data with FAA slot allocation records and in so doing will correct 

discrepancies or errors. However, FAA does not fully verify the 

accuracy of airlines’ self-reported data. Furthermore, FAA does not 

Slot Usage Rate Compliance
 

Page 35 GAO-12-902 Airport Slot Controls

require a specific format for airlines’ usage reports. Therefore, some 

reports are received in a database format that can be entered into 

FAA’s slot management system through an automated interface. 

Others require FAA to manually enter data from a spreadsheet into its 

system. In some cases, FAA officials told us that if extensive reporting 

errors or formatting or other administrative changes are needed, they 

may require the airline to submit a supplemental or corrected usage 

report.

• Limitations in FAA’s database: Because of the difficulties in 

calculating usage rates by FAA, we conducted a limited analysis of 

airline schedule data and FAA data to assess the extent to which 

airlines were using their slots. Using slot allocation records for 

scheduled passenger flights provided by FAA for select days and 

matching them against airline flight schedules for those days, we 

examined the extent to which airlines were scheduling their slots. 

Based on our initial analysis, we determined that in one instance at 

least one airline had not met the 80 percent usage requirement at 

Newark.54

 

54Specifically, we found that one or more airlines at Newark scheduled less than 80 

percent of their allocated slots for selected Saturdays in the 2011 summer season. We 

calculated schedule data for the third Saturday of each month of the summer season 

(April, May, June, July, August, September, and October), which represented 7 of the 30 

Saturdays during the 2011 summer season. FAA officials said that the third week of each 

month is most representative of the rest of the month. Of the 7 Saturdays that we 

examined, schedule rates were between 66 percent and 77 percent. Given average 

cancellation rates for Newark and the typical scheduling rates observed for the days that 

we examined, it is practically impossible (though theoretically possible) for all airlines to 

have met the 80 percent usage requirement for all slots on Saturdays in the 2011 summer

season at Newark. 

Although our method of analysis is not the method that 

FAA uses to oversee individual airlines’ compliance with the usage 

requirement, FAA officials agreed that our method could be used to 

assess whether some of the slots were, at times, operated less than 

80 percent of the time. Our method would not gauge individual 

airline’s compliance, but would provide an aggregated check of usage 

by all airlines. FAA officials told us that they were not aware of the 

problem at Newark so they rechecked their slot allocation records and 

realized that the total slot allocation numbers in their data for Newark 

and JFK were inaccurate. Specifically, their records did not account 

for slots that airlines “handback” (i.e., return) to FAA prior to the slot’s 

handback deadline. Airlines at Newark and JFK are allowed to and 

routinely do return to FAA blocks of slots (e.g., specific days of the 

week or short periods of time) that they initially requested and were 
 

Page 36 GAO-12-902 Airport Slot Controls

allocated by FAA but do not intend to operate during the season.55

• Slot trades and leases: FAA’s review is further complicated by the 

number and frequency of slot trades and leases between airlines. 

FAA officials estimate that it records more than 5,000 airline trades or 

leases per season, which are manually entered into its records. 

Furthermore, slot usage is often reported by the slot operator, but the 

slot holder is responsible for complying with the slot usage 

requirement. Therefore, FAA often has to analyze and correct 

differences in data submitted by a slot holder and the slot operator 

(i.e., the lessee).

FAA officials said that they do not always update their slot allocation 

database with the lists of returned slots because it would be too 

resource-intensive and because of limitations in the computer 

software. While removing the handbacks from the allocation numbers 

provided to us increased the airlines’ presumed usage rate above 80 

percent at Newark airport, FAA did not calculate the usage rates with 

the corrected data and thus, could not provide us verification that the 

airlines usage exceeded 80 percent. And, it does not remove our 

concerns regarding the accuracy of FAA’s data or process for 

verifying compliance with the 80 percent rule.

FAA officials acknowledged some inaccuracies in their data and that their 

process is somewhat inefficient, but told us that they have identified 

instances when airlines have not met the 80 percent usage rate and 

required airlines to return the underutilized slots to FAA. In these cases, 

FAA has issued letters to airlines indicating that they had lost rights to 

their slot. Furthermore, FAA officials explained that they are replacing the 

existing software system, which they said will address some of the 

problems we identified in maintaining complete and accurate records and 

make their oversight of airlines’ compliance with the usage requirement 

more efficient. In particular, the new system should reduce the amount of 

data that requires manual entry into their records system. FAA anticipates 

implementing the new system by the end of 2012. However, because the 

system is not yet operational and its design is not finalized, we do not 

know to what extent the new system will improve the accuracy of FAA’s 

records or improve its ability to check airlines’ compliance with the usage 

requirement.

 

55This practice is also common at slot-controlled outside the United States and required 

under the Worldwide Slot Guidelines. The returned slots do not count against the airline’s 

usage rate, so long as they are returned before the handback deadline, which is about 10 

weeks before the start of the season.
 

Page 37 GAO-12-902 Airport Slot Controls

FAA’s administration of the slot rules provides airlines with large slot 

holdings an advantage over those airlines that hold few slots because 

they have more flexibility in meeting the 80 percent usage requirement. 

Specifically, FAA does not require that airlines report the same flight in a 

specific slot over the course of a reporting period, which essentially allows 

airlines that hold multiple slots within a slot period—30 minutes at the 

New York City airports and 1 hour at Reagan National—to apply the 80 

percent usage requirement collectively to their pool of slots within that slot 

period, as opposed to each individual slot. For example, an airline that 

holds 5 slots within one slot period could hold but not operate one of its 5 

slots (20 percent) and still meet the usage requirement if the other 4 were 

used at 100 percent by “rotating” 4 flights across its 5 allocated slots 

during the reporting period. FAA officials told us that they recognize that 

this method of applying the usage requirement provides more flexibility to 

airlines with multiple slots in a slot period, and that although this method 

is not specifically addressed in the slot control rules, it is not prohibited 

either. FAA officials told us that this method is a long-standing custom 

that has evolved within FAA over time. FAA has no written guidance for 

airlines describing the method. Most slot coordinators outside of the

United States oversee compliance with the usage requirement based on 

each slot’s individual usage. Port Authority officials said that measuring 

usage for each individual slot would reduce the incidence of airlines 

holding onto slots that they do not need, making some existing capacity 

available for redistribution. Representatives from four smaller slot-holding 

airlines told us they would favor FAA requiring airlines to apply the usage 

requirement to each individual slot, while representatives from five 

airlines—four of which have larger slot holdings—said they were opposed 

to it because it would reduce their scheduling flexibility. Using the current 

method for measuring usage of an airline’s slot pool within a slot period, 

airlines have an additional incentive to obtain as many slots as possible to 

increase their operating flexibility without necessarily increasing their 

number of operations—which would be an inefficient use of limited airport 

capacity. Port Authority officials told us that airlines in the past have 

announced new air service without obtaining any new slots. However, the 

only way for an airline to add more flights without obtaining more slots is if 

that airline begins using a slot that it was not fully utilizing before. In 

addition, DOJ raised this as a concern in its comments on the US Airways 

and Delta Air Lines proposed slot swap, referring to the practice of 
 

Page 38 GAO-12-902 Airport Slot Controls

airlines using flights on slots that exceed the 80 percent threshold to 

cover for an unused slot in the same slot period as “babysitting”.56

Increasing the minimum usage requirement above 80 percent could also 

result in less capacity going unused. For example, according to Airports 

Council International in Europe, an airport organization that supports the 

European Commission proposal to increase the minimum usage 

requirement in Europe to 85 percent, increasing the slot usage 

requirement would encourage airlines to optimize their use of slots and 

allow slots that are not being used effectively to be returned and 

reallocated. Because airlines operating outside the United States 

generally schedule all of their slots, they tend to operate a higher 

percentage of their slots than in the United States. Even so, 

representatives from the Association of European Airlines told us that 

increasing the required usage rate could result in an unintended 

consequence of having airlines fly more aircraft than consumer demand 

requires on specific routes, and with lower load factors (percent of 

available seats filled with passengers), to meet the higher usage 

requirement. Although most U.S. airline representatives with whom we 

spoke said they opposed increasing the slot usage requirement, 

representatives from two airlines with small slot holdings said they would 

support increasing it and a representative from another airline supported 

increasing it if the new rate did not penalize for cancellations because of 

bad weather and other unforeseeable circumstances. Representatives at 

an airline with a large number of slots said that increasing the slot usage 

requirement above 80 percent would not increase efficiency because it 

would reduce airlines’ flexibility to cope with unforeseeable events such 

as weather, air traffic control delays, or technical problems. On average, 

however, flight cancellations account for less than 2 percent of the total 

scheduled flights (the cancellation rates at the New York City area 

airports are generally higher than the system-wide average) and FAA 

 

56See, DOJ, Comments of the United States Department of Justice on Notice of Petition 

for Waiver of the Terms of the Order Limiting Scheduled Operations at LaGuardia Airport 

and Solicitation of Comments on Grant of Petition with Conditions, (Washington, D.C.:

Mar. 24, 2010).
 

Page 39 GAO-12-902 Airport Slot Controls

may grant waivers to the minimum usage requirement under other 

unusual or unpredictable circumstances.57

Despite limits on airport capacity, flights operated at slot-controlled 

airports—as compared with flights at other like-sized airports that are not 

slot-controlled— 

• tend to use smaller aircraft;

• are, in some instances, flown to the same destination at higher rates 

per day; and

• have lower overall load factors (percentage of available seats filled 

with passengers).

As a result, the level of passenger traffic at these airports is not as great 

as the number of slots could allow and would-be-new entrant airlines that 

could potentially offer lower fares or service to other destinations may be 

shut out of these markets. The potential inefficient use of slots by 

incumbent airlines at the New York City area airports as a way to block 

competitors’ entry to the New York market has been examined before.

Under FAA’s 2006 proposed, but later withdrawn, congestionmanagement rule for LaGuardia, FAA proposed requiring airlines to use 

an average minimum aircraft size. FAA—in explaining its proposal—

indicated that some inefficiencies at LaGuardia were related to airlines 

using smaller aircraft and that increasing the overall number of 

passengers without increasing the number of flights would result in a 

more efficient use of the national airspace system. Although FAA 

ultimately withdrew the proposed average minimum aircraft size 

requirement in 2008, the agency indicated that the concept behind the 

proposed minimum aircraft-size requirement remained valid because 

capacity cannot be considered merely on the basis of the number of 

aircraft being handled by FAA’s Air Traffic Control system.58

 

57At the New York City area airports, FAA may waive the 80 percent requirement in the 

event of a highly unusual and unpredictable condition which is beyond the control of the 

carrier and which affects carrier operations for a period of 5 consecutive days or more. 

The provision applicable to Reagan National provides that such period must be for 9 or 

more days. This provision further provides examples of conditions which could justify 

waiver – weather conditions which result in the restricted operation of an airport for an 

extended period of time or the grounding of an aircraft type. 

In particular, 

58In April 2008, FAA published a supplemental congestion-management rule proposal for 

LaGuardia without the minimum aircraft size requirement. 75 Fed. Reg. 20846 (Apr. 17, 

2008). The final rule for the Congestion Management Rule for LaGuardia, based on the 

supplemental proposal, was issued in October 2008 and rescinded in 2009.

Underutilized Capacity
 

Page 40 GAO-12-902 Airport Slot Controls

FAA cited certain market patterns involving multiple daily flights on small 

aircraft that were not related to the size of the community served, which 

indicated an inefficient use of slots or behavior that stifled competition. 

Similarly, in 2010, when DOJ commented on the competitive aspects of 

the proposed slot swap between Delta Air Lines and US Airways at slotcontrolled Reagan National and LaGuardia, it found that airlines engaged 

in what DOJ referred to as “slot hoarding” by flying excessive frequencies 

or using small planes.59

To examine the extent to which flights at slot-controlled airports use 

smaller aircraft (100 seats or fewer

While the use of smaller aircraft, high 

frequencies, and low load factors may be indications that airlines are 

hoarding slots as a way to keep competitors out of the slot-controlled 

airports, there are also possible market-based explanations for these 

tendencies. Without other evidence of airlines’ motivations, all that can be 

determined is that flights at the slot controlled airports tend to use the 

available capacity more inefficiently than like-sized airports that are not 

slot-controlled. But, given that slots are a scarce resource and interest 

from new entrant airlines is known, this provides sufficient reason to 

improve slot utilization. 

60), we conducted statistical analyses 

using data on aircraft size of scheduled passenger flights between 

domestic, large hub airports.61 We analyzed airline schedule data that 

included, among other things, the scheduled flight date, origin and 

destination of the scheduled flight, and the size of the aircraft. We used 

data from one Thursday each in February 2011 and in August 2011.62

 

59See, Department of Justice, Comments of the United States Department of Justice on 

Notice of Petition for Waiver of the Terms of the Order Limiting Scheduled Operations at 

LaGuardia Airport and Solicitation of Comments on Grant of Petition with Conditions,

(Washington, D.C.: Mar. 24, 2010). In an analysis of aircraft size, DOJ controlled for the 

fact that commuter slots at Reagan National come with a restriction as to the size of the 

aircraft that can be flown.

60For the purpose of this report, we defined “small” aircraft as one that contains 100 seats 

or fewer. We also examined flights for which a “small” aircraft was smaller than or equal in 

size to the median-sized aircraft (124 seats) in the sample of flights used for the model, as 

well as fewer than or equal to 80 seats. 

61For the purposes of this report, we define large hub airports as all FAA-identified large 

hub airports in the United States for calendar year 2010 (the most recent year available for 

this list), excluding Honolulu. Federal law defines a large hub airports as those that have 

at least 1 percent of the passenger boardings. 49 U.S.C. § 40102(29).

62The specific dates we selected were Feb. 10, 2011, and Aug. 11, 2011.

Aircraft Size
 

Page 41 GAO-12-902 Airport Slot Controls

Thursdays are generally considered to be a high-demand day, and 

February and August are representative months for the winter and 

summer seasons, respectively.

Our analysis indicates that the proportion of flights using small aircraft is 

significantly greater at the slot-controlled airports than at other large hub 

airports that are not slot-controlled. The proportion of flights using small 

aircraft at slot-controlled airports ranged from 36 percent at LaGuardia to 

25.8 percent at Newark, whereas the proportion of flights using small 

aircraft to and from large hub airports that are not slot-controlled was 16.4 

percent. That is, the percent of flights using small aircraft at any of the 

slot-controlled airports was between 9.4 percent and 19.6 percent 

higher—depending on the airport—than the percent of flights using small 

aircraft at other non-slot-controlled large hub airports. We found that 

these differences were all statistically significant (see table 5). To some 

extent, the perimeter rules at Reagan National and LaGuardia contribute 

to the use of smaller aircraft at these airports because shorter haul flights 

are generally served by smaller aircraft, but also limit service to larger 

long-distance markets that use larger aircraft. Also, 11 out of the 60 

hourly slots allowed under the High Density Rule slots at Reagan National 

are reserved for and require the use of smaller aircraft used for commuter 

flights. And, under LaGuardia’s temporary order, FAA assigned some 

slots to airlines that held slot exemptions granted under AIR-21, which 

included slot exemptions for flights serving small communities using 

aircraft with fewer than 71 seats. See appendix V for a detailed 

discussion of our analysis and the results.
 

Page 42 GAO-12-902 Airport Slot Controls

Table 5: Percentage Difference in Flights at Slot-Controlled Airports That Use Small 

Aircraft Compared with Flights at Non-Slot-Controlled Airports, 2011

Airport(s)

Percentage of flights 

that use small 

aircraft 

Percentage differences in small 

aircraft at slot-controlled airports 

compared with other large hub 

airports that are not slot-controlled

Newark

a

25.8 percent 9.4 percent more

JFK 26.6 percent 10.2 percent more

Reagan National 34.0 percent 17.6 percent more

LaGuardia 36.0 percent 19.6 percent more

All 4 U.S. slotcontrolled airports 29.3 percent 12.9 percent more

All 3 New York City 

area slot-controlled 

airports

30.2 percent 13.8 percent more

Large hub airports that 

are not slot controlled

16.4 percent N/A

Source: GAO analysis of airline schedule data.

N/A = not applicable. 

a

The percentage differences are all statistically significant. 

To better understand the extent to which small aircraft are used at slotcontrolled airports, we also developed a logistic regression model that 

controlled for other factors that are likely associated with aircraft size.63

The model assessed whether scheduled passenger flights to or from slotcontrolled airports tend to have a greater likelihood of being scheduled 

with small aircraft compared with flights to and from other large hub 

airports that are not slot-controlled. In addition, the model controlled for 

other factors that include (1) whether the origin or destination of the flight 

is a high-tourism airport,64

 

63A logistic regression (or logit model) provides an indication of which independent 

variables are correlated with the dependent variable—which in this case, is a flight using a 

small aircraft. Moreover, it provides this measure of correlation independent of the effects 

of the other independent variables included in the model. It is important to note, however, 

that this type of statistical method only suggests correlations between variables and not 

causation. That is, our findings do not provide an indication that any of the independent 

variables we included in the model actually caused (or did not cause) an airline to use a 

small aircraft for a flight, but only how those variables are correlated with the use of a 

small aircraft.

(2) whether the airline marketing the flight is a 

64We defined Fort Lauderdale and Orlando, Florida, and Las Vegas, Nevada, as hightourism airports.
 

Page 43 GAO-12-902 Airport Slot Controls

“legacy” airline,65 (3) the daily frequency of flights to the same destination 

by the same airline, and (4) the flight distance. Although the model 

controls for distance, which helps control the effect of the perimeter rules 

at Reagan National and LaGuardia, the model does not control for the 

designated commuter slots at Reagan National that are limited to 

commuter-sized aircraft.66

Similar to our analysis discussed above, the model results also suggest 

that airlines are more likely to use small aircraft for flights at slotcontrolled airports than they are for flights at other large hub airports that 

are not slot-controlled. Specifically, when controlling for other factors that 

may be associated with using a small aircraft, flights to or from the four 

slot-controlled airports are between 22 percent and 108 percent more 

likely—depending on the airport—to use a small aircraft than flights that 

arrive and depart large hub airports that are not slot-controlled (see table 

6). See appendix V for a detailed discussion of the model results.

However, FAA officials told us that based on 

their analysis, about 30 to 40 percent of slots that do not require the use 

of commuter aircraft also use commuter-sized aircraft. Also, as with any 

regression model, this analysis does not prove a causal relationship 

between different factors, such as slot control rules and an airlines’ use of 

a small aircraft. Thus, the extent to which the slot-control rules, the 

perimeter rules at Reagan National and LaGuardia, and the commuterslot designation at Reagan National contribute to underutilization at these 

airports is unknown. Other factors related to the use of small aircraft may 

not be fully controlled for, such as the type of passenger traffic. See 

appendix V for a detailed discussion of the model.

 

65The airlines classified as “legacy” included Delta Air Lines, United Airlines, American 

Airlines, US Airways, and Continental Airlines. Legacy (sometimes called network) airlines 

support large, complex hub-and-spoke operations with thousands of employees and 

hundreds of aircraft (of various types), with flights to domestic communities of all sizes as 

well as to international destinations. The modifier “legacy” derives from the fact that these 

airlines were operating when the industry deregulated in 1978.

66Under federal statute and FAA slot control regulations applicable to Reagan National, 

“commuter slots” may be used only for operations with turboprop and reciprocating engine 

aircraft with no more than 76 seats or turbojet aircraft with fewer than 56 seats.
 

Page 44 GAO-12-902 Airport Slot Controls

Table 6: Percentage Difference in Likelihood of a Flight’s Using Small Aircraft at 

Slot-Controlled Airports Compared with Non-Slot-Controlled Airports

Slot-controlled airport(s)

Likelihood (as measured by odds ratio)a

Newark

that a flight to or from a slot-controlled 

airport used a small aircraft compared with 

other large hub airports that are not slotcontrolled

22 percent more likely

JFK 

b

63 percent more likely

Reagan National

c

72 percent more likely

LaGuardia

c

108 percent more likely

All 4 U.S. slot-controlled airports

c

75 percent more likely

All 3 New York City area slot-controlled 

airports

c

68 percent more likely

Source: GAO analysis of airline schedule data.

c

Notes: The results of our analyses for 124 seat and 80 seat cutoffs also found odds ratio values 

greater than 1, and in some instances the results were more significant. 

The percentage differences in the likelihood that a flight used a small aircraft presented here are 

based on odds ratios calculated from our model. Specifically, the likelihood equals the odds ratio 

minus 1, then multiplied by 100. 

a

See appendix V for a description of odds ratios. 

b

Statistically significant at p-value <0.1. 

c

Statistically significant at p-value <0.01. 

According to representatives from some airlines with smaller slot holdings 

and some airport representatives, airlines with large slot portfolios have 

an incentive and the ability to fly smaller and more frequent flights at slotcontrolled airports in a desire to hold on to slots they would otherwise not 

use because they do not want to lose them to a competitor. Of the 11 

airlines that we interviewed for this review, representatives from 7 nonlegacy airlines favored establishing minimum aircraft size requirements at 

the slot-controlled airports, while representatives from 3 legacy airlines 

opposed it.67

 

67Representatives from the remaining airline did not oppose establishing a minimum 

aircraft size, but did not believe that it was the best method to incent airlines to use larger 

aircraft. 

Representatives from two airlines also said they would 

support a minimum aircraft size requirement if small aircraft could still be 

used to serve small communities. Representatives from two airlines who 

favored establishing a minimum aircraft size said that using small aircraft 

between major markets is a particularly inappropriate use of constrained 
 

Page 45 GAO-12-902 Airport Slot Controls

airspace. However, representatives from legacy airlines that we spoke 

with said establishing minimum aircraft size requirements would 

negatively affect service to small- and medium-sized markets and that it 

would limit their ability to use aircraft sizes that are most appropriate to 

meet customer needs, for example, regarding schedule frequency and 

market conditions. 

In analyzing airline schedule data, we found instances when airlines 

scheduled flights to or from slot-controlled airports for the same 

destination at a more frequent rate than other large hub airports that are 

not slot-controlled. For example, airlines might fly smaller aircraft at 

higher rates to provide frequent shuttle service for business travelers. We 

found, however, that on February 11, 2011, one airline scheduled more 

than 20 daily flights from LaGuardia to Philadelphia—a distance of 96 

miles by air—and that some of those flights were scheduled 10 minutes 

or less apart. As of June 21, 2012, the airline had reduced the number of 

daily nonstop flights on this route to 15. Representatives from the airline 

operating these flights said the high frequency of flights between 

LaGuardia to Philadelphia is driven by consumer demand and provides 

more choice for customers. They also said that almost all of the 

passengers on these flights are connecting to other flights and that the 

airline is not competing with other airlines in this market, but with cars and 

trains. To better understand the extent to which airlines schedule flights to 

or from slot-controlled airports for the same destination at short intervals, 

we examined the frequency of scheduled flights to the same destination 

by the same airline between all large hub airports for one day in February 

2011.68 February is a low demand month in which airlines at slotcontrolled airports might not reduce the number of scheduled flights as 

they might at other airports that are not slot-controlled. Rather, the airline 

might operate smaller, more frequent flights to meet the 80 percent usage 

requirement.69

 

68We examined airline schedule data for scheduled domestic passenger flights for Feb. 

10, 2011.

Our analysis found that of the scheduled flights to or from 

the same destination by the same airline within 15 minutes of one 

another, LaGuardia accounted for 17 of the 50 total scheduled flights 

identified (34 percent). The airport with the next highest proportion was 

Philadelphia International with 11 of the 50 identified flights (22 percent) – 

69FAA’s 80 percent minimum usage requirements pertain to how often a slot is used and 

not size or capacity of the aircraft using the slot. 

Flight Frequency
 

Page 46 GAO-12-902 Airport Slot Controls

all of which were scheduled to fly to or from LaGuardia. Moreover, the 11 

scheduled flights that we identified within 15 minutes of one another 

operated by the same airline between LaGuardia and Philadelphia had an 

average aircraft size of 38 seats. When we examined scheduled flights 

within 30 minutes of one another to or from the same destination by the 

same airline, LaGuardia still had the highest share with 70 of the 264 

identified flights (27 percent), followed by Philadelphia International with a 

share of 29 of the 264 identified flights (see fig. 4). While current slot 

control rules do not prohibit airlines from this type of scheduling practice, 

FAA officials noted that the slot swap between Delta Air Lines and US 

Airways have enabled these airlines to use their resources more 

efficiently. Port Authority officials told us that they believe that any airline 

that schedules a second flight to the same destination within a slot period 

(30 minutes at the New York City area airports) should have to 

demonstrate that there is demand for that second flight that could not be 

met by a single larger aircraft. 
 

Page 47 GAO-12-902 Airport Slot Controls

Figure 4: Airports’ Share of Scheduled Flights to or from the Same Destination by the Same Airline within 15 Minutes or 30 

Minutes of One Another, February 2011

Notes: “Other” airports in the 15 minute chart include Charlotte/Douglas International, Chicago 

O’Hare International, Dallas-Fort Worth International, Las Vegas McCarran International, Newark, 

and San Diego International. 

“Other” airports in the 30 minute chart include Hartsfield-Jackson Atlanta International, Boston Logan 

International, BWI, Charlotte/Douglas International, Dallas-Fort Worth International, Denver 

International, Detroit Metro Wayne County, Dulles, Las Vegas McCarran International, Los Angeles 

International, Orlando International, Miami International, Newark, Phoenix Sky Harbor International, 

Reagan National, San Diego International, San Francisco International, and Tampa International. 
 

Page 48 GAO-12-902 Airport Slot Controls

We also examined FAA data on average load factors (percentage of 

seats occupied) at large hub airports for all domestic scheduled 

passenger flights in calendar year 2011 and found that flights at slotcontrolled airports were overall less full than flights at other large hub 

airports that are not slot-controlled. As shown in figure 5, we found that 

Reagan National (70 percent) and LaGuardia (72 percent) had the lowest 

average load factors for 2011 among the large hub airports, with Newark 

(77 percent) tied with Boston Logan International and Philadelphia 

International for the third lowest load factor.

Figure 5: Average Load Factors at Large Hub Airports for Scheduled Flights during 2011

Load Factors
 

Page 49 GAO-12-902 Airport Slot Controls

According to Port Authority officials and some airline representatives, 

some airlines at slot-controlled airports might operate flights with lower 

load factors to help meet the 80 percent usage requirement and maintain 

control of their slots, whereas flights with similarly low load factors at a 

non-slot-controlled airport might be discontinued. However, another factor 

to explain the comparatively low load factors at New York airports is the 

relatively high airline yields (a measurement of airline revenue per mile). 

Yields at Newark, LaGuardia, and Reagan National are some of the 

highest among the large hub airports, which means that a flight with a low 

load factor may still be profitable for these airlines. If the objective is to 

maximize the number of passengers at these airports, however, this 

represents an inefficient use of airport capacity.

Representatives from low cost and other airlines that have sought to 

obtain slots told us that they have had difficulty gaining access to slotcontrolled airports. Airline representatives seeking slots at these airports 

told us that they have spoken to FAA, but generally not enough slots are 

available or the slots are at undesirable times of day (e.g., early morning 

or late evening) for these airlines to operate profitable service.70 DOT 

officials are also aware of the access issue, and it was a focus of the 

previous congestion-management rulemakings and an advisory Aviation 

Rulemaking Committee report for the New York City area airports.71

 

70One airline representative told us that the airline would need enough slots for three 

transcontinental flights per day to be profitable.

DOT 

also took steps to mitigate potential competitive harm from the Delta Air 

Lines and US Airways proposed slot swap by requiring divestiture of 

some slots at the airports to airlines with small or no presence at the 

airports. DOJ, in commenting on competition at LaGuardia and Reagan 

National during the Delta Air Lines and US Airways proposed slot swap in 

2010, indicated that the lack of availability of slots is a substantial barrier 

to entry at those airports, especially for low cost airlines. Based on 

literature that we reviewed, airfares can drop up to 30 percent on a flight 

route as a result of a low cost airline entering the airport and beginning 

71New York Aviation Rulemaking Committee Report, December 13, 2007.

Slot Control Rules Limit 

New Entry and Hinder 

Competition
 

Page 50 GAO-12-902 Airport Slot Controls

service on that route.72

Figure 6: Proportion of Legacy and Other Airline Passenger Traffic at Slot-Controlled and Non-Slot-Controlled Large Hub 

Airports, 2011

Because average airfares at the slot-controlled 

airports are some of the highest among domestic large hub airports, the 

entrance of low cost competition could be helpful in bringing down 

airfares at those airports. While in some cases Congress has directed 

that new airport capacity in the form of slot exemptions be allocated to 

new entrants or “limited incumbents,” which are generally low cost 

airlines, those new slot exemptions are a small percentage of the total 

slots at the airport. Figure 6 shows that the proportion of passenger traffic 

handled by the nonlegacy airlines in 2011 generally is smaller at slotcontrolled airports compared with the other 24 large hub airports.

DOJ also indicated in 2010 that increasing the number of slots held by 

two large legacy carriers at the slot-controlled LaGuardia and Reagan 

National airports would make it more difficult for new entrants to obtain 

slots because large legacy carriers would have greater incentives to 

 

72See Steven A. Morrison, “Actual, Adjacent, and Potential Competition: Estimating the 

Full Effects of Southwest Airlines,” Journal of Transport Economics and Policy, Vol. 35, 

part 2, May 2001, and Austan Goolsbee and Chad Syverson, “How Do Incumbents 

Respond to the Threat of Entry? Evidence from the Major Airlines,” The Quarterly Journal 

of Economics (2008). 
 

Page 51 GAO-12-902 Airport Slot Controls

forestall entry by refusing to sell or lease their slots. Representatives of 

some airlines with few slot-holdings told us that they believe that the 

airlines that hold the majority of slots at the airports are hesitant or 

unwilling to lease to them. In general, airlines holding a slot under FAA’s 

slot rules may lease or trade slots to other airlines and can select which 

airlines they lease or trade slots with.73

According to Port Authority officials and some airline representatives, if 

FAA were to limit the length of time that an airline could hold on to a slot 

when that airline was not using or leasing it to another airline—after which 

the slots would be withdrawn by FAA for reallocation—this could provide 

opportunities for new entrants or small slot-holders to obtain slots. 

Representatives from most of the airlines we contacted, except the legacy 

airlines, said they favored limiting how long airlines can hold onto slots 

they are not using. However, representatives from a legacy airline said 

that imposing such a holding limit is unnecessary because slots do not go 

unused. These representatives told us that although there are some 

instances that on paper it appears that airlines are not using their slots, 

the airlines are actually holding the slots by leasing them to other airlines 

for a future time when they want to use them again. Also, the 

Airlines may have legitimate 

business reasons for leasing slots to code-share partners, for example, to 

feed into the lessor airlines’ network. In addition, representatives from 

large slot-holding airlines said that they may hold onto slots that they do 

not currently need by leasing to other airlines in case they want them 

back later. In general, airlines only return slots to FAA that airlines are 

unable to find other airlines interested in leasing or buying. Airlines with 

large slot holdings also noted that they have made substantial financial 

investments in terminal facilities, such as terminals at JFK, at the slotcontrolled airports. While the slots that are returned can be reallocated to 

other airlines, including new entrants or limited incumbents, the returned 

slots generally are the least desirable—such as early morning or late 

evening or weekend-only—and may only be for a couple of months, 

which makes them undesirable for airlines trying to build year-round 

service.

 

73Under FAA’s slot control orders for JFK, LaGuardia, and Newark, slots may not be 

bought or sold but may be leased or traded through the effective date of the orders, or 

relinquished to FAA. Under FAA slot regulations for Reagan National, slots may be 

bought, sold, leased, or traded, with the exception of slot exemptions, which may not be 

bought, sold, leased, or otherwise transferred, except through an air carrier merger or 

acquisition. 49 U.S.C. 41714(j).
 

Page 52 GAO-12-902 Airport Slot Controls

representatives noted that airlines may be holding onto slots for long 

periods of time (e.g., over multiple seasons) because the temporary slot 

orders for the New York City area airports do not allow airlines to buy or 

sell slots.

FAA’s administration of its slot rules can hinder the ability of airlines to 

add service at slot-controlled airports because it does not provide 

complete transparency about what slots are available. FAA officials said 

that, upon request, FAA provides airlines with lists of slot holders and 

operators as well as available slots, but some airline representatives and 

Port Authority officials told us that the format of this information does not 

make clear what slots are available. Furthermore, as discussed earlier, 

because of discrepancies in FAA’s slot allocation records, it is unclear 

whether the information provided to airlines is accurate. Port Authority 

officials recommend public reporting of slot leasing and slot usage, 

including the reasons why the slots are not being operated (e.g., flights 

were not scheduled or were cancelled) to provide transparency of 

information. In addition, although FAA requires the submission of certain 

records of all trades and leases between airlines, it does not require the 

submission of the information—such as the origin and destination that a 

lessee intends to use for the slot—that would allow FAA or DOT to 

monitor the extent to which leases occur between nonpartner airlines.74

While DOT officials questioned the efficacy of reviewing data currently 

collected on airline slot leases in isolation, additional information relating 

to the transaction could be helpful. But, officials noted that even with 

additional data, the department faces a very high burden of proof in 

alleging that an airline is engaged in unfair or deceptive competitive 

practices.75

 

74Airlines partner with other airlines on some routes and not others. Under current slot 

control rules, airlines are not required to provide FAA copies of slot leases (or any 

information regarding consideration for slots transferred). FAA slot control orders for JFK, 

LaGuardia, and Newark require airlines to submit notice of a slot trade or lease to FAA in 

writing. Such trades or leases are subject to the confirmation and approval of FAA. The 

FAA slot-control regulations for Reagan National provide, in part, that requests for FAA 

confirmation of transfers, including leases, shall include the names of the transferor and 

recipient; whether the slot is to be used for an arrival or departure; the date the slot was 

acquired by the transferor; whether the slot has been used by the transferor for 

international or essential air service operations; and whether the slot will be used by the 

recipient for international or essential air operations, among other things. A recipient may 

not use a transferred slot without written confirmation from FAA.

DOT officials told us that they believe that under the current 

75Under 49 U.S.C .§ 41712, DOT may investigate whether airlines have engaged in

“unfair and deceptive practices and unfair methods of competition.” 
 

Page 53 GAO-12-902 Airport Slot Controls

temporary orders, they are unable to react to certain market failures at 

slot-controlled airports, such as inefficient use of constrained airspace. 

DOT officials could not comment further on this because of the pending 

Slot Management and Transparency rulemaking for the New York City 

area airports. DOJ officials told us that, unless they have an open 

investigation, they do not monitor ongoing day-to-day activities such as 

short-term leases at slot-controlled airports. An investigation of 

competition-related issues at these airports is generally “triggered” by a 

transaction such as an airline merger or slot swap, although DOJ may 

also investigate in response to complaints, such as complaints by airlines 

unable to obtain slots. Additional information on leases and trades of 

slots, particularly the relationship between the lessor and the lessee, 

would allow FAA to provide more complete information to airlines on the 

availability of slots, which increases transparency.

Because the New York City airports are both capacity constrained and 

among the nation’s most sought after by airlines to serve, FAA has had to 

institute slot controls to manage congestion and resultant delays. It is 

therefore important that slots allocated to airlines are efficiently utilized, 

thereby maximizing the airports’ available capacity, or reallocated to other 

airlines that will use them efficiently, which could, in turn, provide access 

to new entrant airlines that offer new service destinations and lower fares. 

Despite these goals, we found that considerable existing capacity is not 

being used or is used inefficiently at these airports. Certain aspects of the 

slot control rules, as well as FAA’s administration of them, contribute to 

this situation and, thus, may hinder the ability of some new entrant 

airlines to obtain slots at the four U.S. slot-controlled airports. In 

particular, although the current slot control rules require slot holders to 

operate their slots 80 percent of the time, they do not require slot holders 

to schedule a flight for each of their slots. And, as opposed to airlines 

operating at slot-controlled airports outside the United States that 

generally schedule flights for all of their slots, domestic airlines operating 

at the U.S. slot-controlled airports do not always schedule all of their 

slots, which contributes to capacity going unused. Further, FAA’s current 

recordkeeping and process for reviewing airline slot usage data do not 

provide sufficient assurance that it can adequately identify when airlines 

do not meet the 80 percent usage requirement. Not requiring airlines to 

report usage data in a standard format or having management systems 

that can adequately compile data received in different formats, as well as 

its reliance on airlines’ self-reported data and discrepancies in its slot 

allocation record, hinders FAA’s ability to check compliance with the slot 

usage requirement. Moreover, because FAA does not calculate the actual 

Conclusions
 

Page 54 GAO-12-902 Airport Slot Controls

slot usage rates for airlines, the amount of capacity that goes unused is 

unknown, which limits FAA’s ability to manage slots or set policy for the 

airspace. FAA’s planned upgrades to its slot management software later 

this year will hopefully improve its oversight capabilities, but not without

better and more standardized reporting by airlines. Other practices that 

affect utilization, however, will not be fixed with the new software. For 

example, FAA allows an airline to apply the usage requirement across its 

entire pool of slots within a slot time period, rather than applying the 

requirement to its individual slot—a practice that provides advantages to 

airlines with large slot holdings over those with small slot holdings in 

meeting the requirement. This practice can lead to underutilization of 

individual slots and hinder other airlines’ ability to obtain slots at these 

airports. Limitations in FAA’s recordkeeping, particularly the 

discrepancies in its slot allocation records, as well as its lack of 

information on the relationship between slot lessors and lessees and 

public disclosure on the availability of slots and lease information, also 

hinder access to new entrant airlines at slot-controlled airports.

To help maximize the use of available capacity at slot-controlled airports, 

enhance competition through greater airline access to slots, and enhance 

transparency of slot information, we recommend that the Secretary of 

Transportation direct the FAA Administrator to take the following five 

actions:

• require airlines to report usage data in a standard format at the end of 

each reporting period or ensure that future slot management systems 

have the capability to compile data in different formats;

• periodically calculate the rates at which airlines are scheduling and

using their slots;

• apply slot rules to individual slots, as opposed to pools of slots within 

a slot period;

• periodically disclose information, which may include current slot 

holders and operators, on currently available slots; and

• collect and disclose data, including the relationship between lessors 

and lessees, on slot leases.

Furthermore, with respect to possible future regulatory action, we 

recommend that DOT Secretary consider requiring airlines to schedule a 

certain percentage, or all, of their slot allocations, similar to practices 

maintained elsewhere in the world.

Recommendations for 

Executive Action
 

Page 55 GAO-12-902 Airport Slot Controls

We provided DOT, MWAA, the Port Authority of New York and New 

Jersey, DOJ, and the Department of Homeland Security (DHS) with a 

draft of this report for their review and comment. DOT’s Office of the 

Secretary and FAA provided technical comments that we incorporated as 

appropriate. In addition, in comments e-mailed to us, FAA reiterated that 

the slot control rules at the three New York City area airports and Reagan 

National were adopted primarily to manage congestion and delay at these 

airports by limiting planned operations during peak hours. Officials 

highlighted that complex issues arise with the allocation and use of a 

scarce resource like airport slots and that congestion-management policy 

objectives must be balanced with realistic competition and market access 

goals. FAA indicated that economic and compliance benefits and costs to 

stakeholders and regulatory and statutory guidelines must also be 

considered. We agree that the slot control rules can manage congestion 

and delay and that issues may arise when allocating a scarce resource. 

We also believe that the rules can be improved to make the use of current 

capacity more efficient, as well as enhance competition. Officials also 

noted that DOT’s Office of the Secretary and FAA are developing rules to 

replace the temporary slot control Orders at the New York City area 

airports with more permanent rules. As stated in our report, these 

temporary rules have been extended twice, creating a level of uncertainty 

in the market about when the final rule will be issued and what it will 

contain. While we acknowledge DOT’s and FAA’s efforts to develop a 

permanent rule, we also believe that FAA could take separate action now 

to help maximize the use of available capacity at slot-controlled airports, 

enhance competition through greater airline access to slots, and enhance 

transparency of slot information. 

MWAA provided written comments, which are reprinted in appendix VI. 

MWAA agreed with our recommendations to improve FAA’s oversight of 

slot utilization and encouraged DOT to adopt these recommendations to 

better manage available airport capacity and provide a more transparent 

process. However, MWAA disagreed with our conclusion that the 

additional beyond-perimeter slot exemptions at Reagan National are likely 

to have a limited effect on the Washington, D.C., area airports and can be 

supported by terminal capacity at Reagan National. In the comments, 

MWAA indicated that the impact of the beyond-perimeter flights should be 

viewed in the broader context of other changes under way at Reagan 

National, for example, those resulting from legacy carrier mergers, the 

Delta Air Lines and US Airways slot-swap transaction, and other recent 

commercial slot transactions. MWAA believes that these factors are 

changing the operating character of Reagan National, change that may 

require considerable additional capital investment for extensive facility 

modifications. However, our review was expressly limited to the impact of 

Agency Comments 

and Our Evaluation
 

Page 56 GAO-12-902 Airport Slot Controls

the additional slot exemptions authorized in 2012, and not the cumulative 

effect of previously authorized beyond-perimeter slot exemptions and 

other slot-related and commercial changes. The report includes the views 

of MWAA management with regard to the specific challenges faced by 

the expansion of beyond-perimeter slot exemptions throughout, but our 

overall assessment remains that the effect of the 2012 FAA 

Reauthorization slot exemptions is manageable and that the impact on 

other Washington, D.C., area airports is relatively small. On this point, 

MWAA disagrees with our report in regard to the financial impact of 

potential passenger erosion on Dulles International. Our report does 

recognize the potential effect on per-passenger airline costs at Dulles and 

Reagan National, but also states that this estimated effect is a worst case 

scenario and should be considered in light of (1) the recent substantial 

increases in costs from capital investments at Dulles that are unrelated to 

the new slot exemptions; (2) the passenger growth forecast by FAA that 

could ameliorate that erosion; (3) the views of airlines and credit-rating 

agencies that airline service is also dependent on market demand, which 

is strong in this region; and (4) the “extraordinary coverage protection 

payments” provision in the airline lease agreements that may allow 

MWAA to share debt service between the two airports should they need 

to and the possibility of revising this provision in the new lease. Finally, as 

we indicate in the report, we concur with MWAA that because some of the 

new beyond-perimeter flights only started in August 2012, the actual 

impact of the new beyond-perimeter flights cannot yet be fully 

determined. MWAA also provided some specific updated information, 

which we incorporated as appropriate in the report. 

The Port Authority of New York and New Jersey provided written 

comments, reprinted in appendix VII, agreeing with the report’s 

conclusions and recommendations. The Port Authority of New York and 

New Jersey provided some clarifications that we incorporated as 

appropriate. DHS, on behalf of TSA, also provide some clarifications that 

we incorporated. DOJ provided no comments. 

We are sending copies of this report to interested congressional 

committees and the Secretary of Transportation. In addition, the report is 

available at no charge on the GAO website at http://www.gao.gov.

If you or your staff have any questions about this report, please contact 

me at (202) 512-2834 or flemings@gao.gov. Contact points for our 

Offices of Congressional Relations and Public Affairs may be found on 
 

Page 57 GAO-12-902 Airport Slot Controls

the last page of this report. GAO staff who made major contributions to 

this report are listed in appendix VIII.

Susan A. Fleming

Director, Physical Infrastructure Issues
Appendix I: Objectives, Scope, and 

Methodology

Page 58 GAO-12-902 Airport Slot Controls

In this report, we reviewed (1) the potential effects of increasing the 

number of beyond-perimeter slot exemptions at Reagan National and 

(2) whether slot control rules at the four U.S. slot-controlled airports are 

working to reduce congestion, while maximizing available capacity and 

encouraging competition.

To review the potential effects of increasing the number of beyondperimeter slot exemptions at Reagan National, we

• compared airside capacity assessments with actual usage;

• reviewed terminal space needs;

• assessed the impact on the additional beyond-perimeter flights on 

passenger traffic, capital financing, security screening wait times, and 

noise; and

• interviewed officials from the Federal Aviation Administration (FAA), 

the Metropolitan Washington Airports Authority (MWAA), and the 

Baltimore-Washington International Thurgood Marshall Airport (BWI), 

as well as representatives from airlines1

Regarding airside capacity, we analyzed data on the volume of aircraft 

operations at Reagan National, regulations and FAA actions regarding 

slot allocations at the airport, and a capacity assessment conducted by an 

FAA contractor. With respect to terminal capacity, we observed the 

airport’s baggage handling equipment, gates, ticket counter space, and 

security screening facilities; reviewed usage data on gates and parking 

lots; and discussed plans to expand terminal and security screening 

space with MWAA officials.

and others.

To assess the maximum impact that the new beyond-perimeter flights 

would have on passenger traffic, we assumed that the new flights would 

be 100-percent full and that all passengers would be shifting from Dulles 

to Reagan National. This provided the highest possible estimate of the 

loss of passengers and the associated rise in cost per enplaned 

passenger at Dulles because of the new beyond-perimeter flights at 

Reagan National. However, for a variety of reasons, it is unlikely that the 

number of passengers shifting from Dulles to Reagan National would 

actually be this high. First, the new flights are unlikely to draw travelers 

 

1

To obtain views from airlines on these issues, we contacted 12 airlines that serve 

Reagan National, had applied for beyond-perimeter slot exemptions there, or had 

expressed interest to FAA in serving that airport. Representatives from 11 of the 12 

airlines agreed to talk with us.

Appendix I: Objectives, Scope, and 

Methodology 
Appendix I: Objectives, Scope, and 

Methodology

Page 59 GAO-12-902 Airport Slot Controls

solely from Dulles. For example, consumers who have a strong 

preference for flying out of Reagan National might have been choosing to 

fly from Reagan on a connecting basis but will now have a direct choice 

and, despite the likelihood of a substantially higher fare, some of these 

passengers will opt for the more expensive direct flight. Similarly, some 

travelers might shift to the new flights at Reagan National from BWI.

Second, the availability of the new flights may induce some pricing 

impacts that could influence travelers’ decisions. For example, airlines 

that fly the same routes from Dulles may attempt to maintain their traffic 

by lowering prices on those routes to better compete for passengers who 

now have a nonstop choice from Reagan National. This would likely 

mitigate the flow of passengers from Dulles to Reagan National, and may 

even induce some new travelers on these routes. And finally, although 

the new routes will likely be very popular, it is possible that not all seats 

will be sold indicating that not all seats are filled with passengers who 

would have previously chosen Dulles. For these various reasons, it is 

likely that our “worst case” estimate of the number of passengers shifting 

from Dulles to Reagan National is likely overstated. We did not include 

the within-perimeter flights that were converted to beyond-perimeter slot 

exemptions in our analysis because there were too many unknown 

factors, such as whether the passengers those flights were connecting or 

originating at Reagan National and the load factors on those flights.

Regarding the new beyond-perimeter flights’ impact on capacity 

financing, using our estimate of the number of passengers who could shift 

from using Dulles to Reagan National, we asked MWAA to estimate the 

impact on the cost per enplaned passenger at the two airports. We also 

discussed the methodology that MWAA used and determined that its 

methods were sufficiently reliable for our purposes. We also reviewed 

credit-rating reports on MWAA and discussed the reports with rating 

agency officials. Moreover, we reviewed passenger traffic and airfare and 

Dulles and BWI data relating to the beyond-perimeter flight destinations 

that were added between 2000 and 2004.

With respect to the impact that the new beyond-perimeter flights could 

have on aircraft noise, we reviewed the most recent noise compatibility 

report on Reagan National and noise complaints since 2008 and 

interviewed individuals from community groups concerned about aircraft 

noise at Reagan National as well as officials from the Washington Council 

of Governments, the Arlington County (Va.) Council, MWAA, and FAA.

To assess the impact that the new beyond-perimeter flights could have on 

passenger security screening wait times, we asked the Transportation 
Appendix I: Objectives, Scope, and 

Methodology

Page 60 GAO-12-902 Airport Slot Controls

Security Administration (TSA) to estimate, using its security screening 

throughput model, how the wait time would be affected. As inputs to the 

model, we provided TSA with the flight times for the new beyondperimeter flights, data on the maximum number of passengers on those 

flights, and the screening checkpoints that the passengers would use. We 

did not report the precise estimates of wait time changes because they 

would imply a greater level of precision than the model could reasonably 

provide.

To review whether slot controls at U.S. slot-controlled airports are working 

to reduce congestion, while maximizing available capacity and 

encouraging competition, we analyzed airline schedule data and FAA slot 

allocation data to determine the rate at which slots at slot-controlled 

airports are scheduled. We also analyzed and compared and contrasted 

airline schedule data on aircraft size and flight frequency and Department 

of Transportation (DOT) data on average annual load factors and 

passenger traffic at the four slot-controlled airports with the remaining 

large hub airports2

 

2

For the purposes of this review, we defined large hub airports as all FAA-identified large 

hub airports in the United States for calendar year 2010 (the most recent year available for 

this list), excluding Honolulu. Federal law defines large hub airports as those commercial 

service airports that have at least 1 percent of the passenger boardings. 49 U.S.C. § 

40102(29). The large hub airports included in our study are: Hartsfield-Jackson Atlanta 

International, Boston Logan International, Baltimore-Washington International Thurgood 

Marshall, Charlotte/Douglas International, Ronald Reagan Washington National, Denver 

International, Dallas-Fort Worth International, Detroit Metro Wayne County, Newark 

Liberty International, Fort Lauderdale-Hollywood International, Dulles International, 

George Bush Intercontinental, John F. Kennedy International, Las Vegas McCarran 

International, Los Angeles International, LaGuardia International, Orlando International, 

Chicago Midway, Miami International, Minneapolis-St. Paul International, Chicago O’Hare 

International, Philadelphia International, Phoenix Sky Harbor International, San Diego 

International, Seattle-Tacoma International, San Francisco International, Salt Lake City 

International, and Tampa International.

that are not slot-controlled. We interviewed officials 

from DOT; FAA; Department of Justice (DOJ); MWAA; and the Port 

Authority of New York and New Jersey, and interviewed representatives 

from 11 airlines that currently serve or have interest in serving one or 

more U.S. slot-controlled airport. We also contacted other stakeholders, 

including representatives from Airlines For America; the International Air 

Transport Association; Airports Council International, North America; and 

others, about slot control issues. We also reviewed slot control 

regulations for the four U.S. slot-controlled airports and obtained and 

analyzed applicable federal laws, regulations, and agency orders. In 
Appendix I: Objectives, Scope, and 

Methodology

Page 61 GAO-12-902 Airport Slot Controls

addition, we reviewed studies on airline competition, airport capacity, and 

demand management measures, including slot controls, as well as the 

slot reform proposal for the European Union and the Worldwide Slot

Guidelines.

To calculate the rate at which slot allocations for scheduled passenger 

flights are scheduled at slot-controlled airports, we divided the total daily 

scheduled passenger flights within slot-controlled hours for a specific day 

and airport by the total number of daily slot allocations (provided by FAA) 

for that day and airport. We obtained airline schedule data from Innovata 

for scheduled passenger flights for the third week of February and August 

2011 for JFK, Newark, LaGuardia, and Reagan National. FAA provided 

the daily total slot allocation numbers for scheduled passenger flights 

during slot-controlled hours for the same days for JFK, Newark, 

LaGuardia, and Reagan National.3

To examine whether flights at slot-controlled airports use smaller aircraft, 

we conducted statistical analyses, including the construction of a logistic 

regression model to assess whether flights at slot-controlled airports use 

smaller aircraft than flights at other large hub airports that are not slotcontrolled, while controlling for other factors that are likely associated with 

aircraft size, such as the flight distance (see app. V for more details on 

our model and results). We analyzed Innovata airline schedule data for 

FAA officials told us that the third 

week of the month is most representative of the month. To further 

examine schedule rates at Newark, we also obtained and analyzed daily 

slot allocations and airline schedule data for the third Saturday of April, 

May, June, July, September, and October 2011 for Newark. During our 

review FAA reported discrepancies in the slot allocation numbers 

provided to us. Specifically, FAA does not systematically update their slot 

allocation records with the lists of returned slots received from airlines 

each season for JFK and Newark. As a result, the data on slot allocations 

used for our analysis for JFK and Newark generally represents the 

number of flights initially allocated to each airline for the season rather 

than the final number they held.

 

3

From the total slot allocations numbers, FAA removed all UPS and FedEx cargo 

operations from the totals. Additionally, FAA only provided slot totals for those assigned 

during slot-controlled hours. At JFK and Newark, slot-controlled hours are 6:00 a.m. to 

10:59 p.m. Eastern Time. At LaGuardia, slot-controlled hours are 6:00 a.m. to 9:59 p.m. 

Eastern Time, Monday through Friday, and 12:00 p.m.to 9:59 p.m. Eastern Time on 

Sunday. At Reagan National, the airport is slot-controlled 24 hours a day, but we 

examined high-demand hours, which are from 7:00 a.m. to 9:59 p.m. Eastern Time.
Appendix I: Objectives, Scope, and 

Methodology

Page 62 GAO-12-902 Airport Slot Controls

one Thursday each in February 2011 and in August 2011.4 Thursdays are 

generally considered to be a high-demand day, and February and August 

are representative months for the winter and summer seasons, 

respectively. We calculated the proportion of scheduled passenger flights 

arriving or departing each large hub airport that use aircraft with 100 

seats or fewer. We also compared and contrasted the proportion of flights 

using aircraft with 100 seats or fewer departing or arriving slot-controlled 

airports with other large hub airports that are not slot-controlled. We 

tested that the difference was statistically significant. Since a variety of 

factors, in addition to slot controls, may be correlated with the use of a 

small aircraft, we developed a logistic regression model. The model 

assessed whether flights to or from slot-controlled airports used an 

aircraft with 100 seats or fewer compared with flights that arrive and 

depart other large hub airports that are not slot-controlled, while 

controlling for other factors that include (1) whether the origin or 

destination of the flight is a high-tourism airport,5 (2) whether the airline 

marketing the flight is a legacy airline,6

To examine closely-scheduled flights to the same destination by the same 

airline, we analyzed airline schedule data, obtained from Innovata, for all 

flights arriving or departing FAA-identified large hub airports on Thursday 

February 10, 2011. For this analysis we calculated the number of minutes 

between each flight and the flight immediately prior to and following on 

the same route and by the same airline. We then identified those flights 

with another flight less than or equal to15 or 30 minutes apart, and 

calculated the proportion of such flights from each airport.

(3) the daily frequency of flights to 

the same destination by the same airline, and (4) the flight distance. We 

also conducted alternative scenarios examining aircraft with 124 seats or 

fewer (the median-sized aircraft in our sample) and 80 seats or fewer. 

See appendix V for more details on the logistic regression model and 

results.

 

4

The specific dates we selected were Feb.10, 2011, and Aug. 11, 2011.

5

We defined Fort Lauderdale and Orlando, Florida, and Las Vegas, Nevada, as hightourism airports.

6

The airlines classified as legacy included Delta Air Lines, United Airlines, American 

Airlines, US Airways, and Continental Airlines. Legacy (sometimes called network) airlines 

support large, complex hub-and-spoke operations with thousands of employees and 

hundreds of aircraft (of various types), with flights to domestic communities of all sizes as 

well as to international destinations. The modifier “legacy” derives from the fact that these 

airlines were operating when the industry deregulated in 1978.
Appendix I: Objectives, Scope, and 

Methodology

Page 63 GAO-12-902 Airport Slot Controls

Average annual load factor data and average annual airline yield data for 

large hub airports was obtained from DOT’s T-100 database, which 

includes operational data collected from airlines and DOT’s origin and 

destination survey, respectively. To calculate airlines’ proportion of 

passenger traffic on domestic scheduled passenger flights, we obtained 

and analyzed data from DOT’s origin and destination survey for 2011 at 

each of the large hub airports.

To assess the reliability of airline schedule data, and DOT’s T-100 and 

origin and destination survey, we (1) reviewed existing documentation 

related to the data sources and (2) interviewed knowledgeable agency 

officials and representatives about the data. We determined that the data 

were sufficiently reliable for the purposes of this review.
Appendix II: Comparative Information on Major 

Airports in the New York City and Washington, 

D.C., Area

Page 64 GAO-12-902 Airport Slot Controls

Airport JFK LaGuardia Newark

Reagan 

National Dulles BWI

Location Queens County, 

NY, 15 miles 

from midtown

Manhattan

Borough of 

Queens, New 

York City, 

8 miles from 

midtown 

Manhattan

Newark and 

Elizabeth, NJ, 

14 miles from 

Manhattan

Arlington County, 

VA, 3 miles from 

downtown 

Washington, 

D.C.

Chantilly, VA, 

26 miles from 

downtown 

Washington, 

D.C.

Anne Arundel 

County, MD, 10 

miles south of 

Baltimore and 32 

miles north of 

Washington, 

D.C.

Operator Port Authority of 

New York and 

New Jersey

Port Authority of 

New York and 

New Jersey

Port Authority of 

New York and 

New Jersey

Metropolitan 

Washington 

Airports Authority

Metropolitan 

Washington 

Airports Authority

Maryland 

Department of 

Transportation’s 

Aviation 

Administration

Acres of land 4,930 680 2,027 733 11,830 3,596

Number of 

runways

4 

14,572 feet 

11,351 feet 

10,000 feet 

8,400 feet

2 

both are 7,000 

feet

3 

11,000 feet 

9,980 feet 6,800 

feet

3 

6,869 feet 5,204 

feet 4,911 feet

4 

2 are 11,500 feet

10,500 feet 

9,400 feet

4 

10,502 feet 

9,501 feet 6,000 

feet 5,000 feet 

Number of gates 124 a 76 115 44 139 68

Number of 

airlines

77 a 17 28 11 29 11

Airline holding the 

most slots

Delta Air Lines

(33 percent) b Delta Air Lines

(44 percent)

United Airlines 

(75 percent)

US Airways 

(54 percent)

United Airlines

(73 percent)c

Southwest 

Airlines

(57 percent)

2010 

enplanements 

c

22,892,372 11,988,578 16,542,619 8,726,183 11,251,041 10,770,973

2011 

enplanements

23,585,722 11,983,322 16,786,357 9,039,072 11,020,479 10,985,559

Change in 

enplanements 

from 2010 to 2011

3 percent 0 percent 1.5 percent 3.6 percent (2 percent) 2 percent

Domestic share 

of 2011 

enplanements

50 percent 96 percent 66 percent 98 percent 72 percent 98 percent

Sources: MWAA, Port Authority of New York and New Jersey, BWI, and BTS.

a

As of June 2012. 

b

As of May 15, 2012. 

c

Appendix II: Comparative Information on 

Major Airports in the New York City and 

Washington, D.C., Area 

Because Dulles and BWI are not slot-controlled airports, the data reflect the airlines’ percentage of 

total scheduled departures on May 15, 2012, rather than the percentage of slots held. 
Appendix III: History of Slot Control Rules and 

Related Actions

Page 65 GAO-12-902 Airport Slot Controls

Slot controls at Reagan National and the New York City area airports 

were first implemented in the late 1960s. Since then, the number of 

takeoffs and landings permitted at these airports has been revised 

periodically as well as the slot control procedures that airlines should 

follow. In addition, since the 1950s at LaGuardia and since the 1960s at 

Reagan National, airlines have been subject to limitations on the distance 

of their nonstop flights known as “perimeter rules.” Figure 7 shows when 

major events related to slot controls and perimeter rules occurred at the 

four airports. 

Appendix III: History of Slot Control Rules 

and Related Actions
Appendix III: History of Slot Control Rules and 

Related Actions

Page 66 GAO-12-902 Airport Slot Controls

Figure 7: Timeline of Major Actions Taken Regarding Slot Controls and Perimeter Rules at the Major New York City Area 

Airports and Reagan National

Slot controls were implemented in 1969 when the Federal Aviation 

Administration (FAA) designated JFK, LaGuardia, Newark, Chicago 
Appendix III: History of Slot Control Rules and 

Related Actions

Page 67 GAO-12-902 Airport Slot Controls

O’Hare, and Washington National1 as high density airports. In 

implementing what became known as the High Density Rule, FAA 

indicated that slot controls were needed to provide relief from excessive 

delays at these airports.2 Under the rule, FAA required airlines to obtain 

slots to operate during certain hours at those airports and initially imposed 

limits of 60 takeoffs and landings per hour at Newark, LaGuardia, and 

Washington National, and 80 per hour at JFK. In 1970, FAA lifted the 

High Density Rule at Newark because of a lower level of usage of the 

slots at that airport as evidenced by, among other things, that the average 

number of aircraft operations at peak hours was 18 less than the 60 slots 

allowed.3 In general, Newark was not slot-controlled from late October 

1970 until 2008.4 FAA implemented the High Density Rule in 1969 and, 

because of its effectiveness in reducing congestion and delays, extended 

it for an indefinite period of time in 1973. Airline scheduling committees, 

operating under then-authorized antitrust immunity, conferred by the Civil 

Aeronautics Board, initially allocated the slots. However, according to 

FAA officials, after the Airline Deregulation Act of 1978 was enacted into 

law,5 increased airline competition made it more difficult for the 

scheduling committees to agree on slot allocations and antitrust immunity 

for the committees’ operations expired under the terms of the Airline 

Deregulation Act. In 1986, as a part of its High Density Rule, FAA 

replaced the scheduling committees with slot procedures such as 

providing for the withdrawal of slots not used at least 65 percent of the 

time, the voluntary return of slots, the reallocation of withdrawn and 

returned slots, and allowing airlines to buy, sell, or lease their slots.6

 

1

Slot controls at Chicago O’Hare Airport expired in 2002. In 1998, Washington National 

Airport was renamed Ronald Reagan Washington National Airport.

In 

implementing this 1986 minimum slot usage rule, FAA cited the 

Department of Justice’s (DOJ) concerns that a use or lose provision “may 

be necessary to prevent large carriers or several large carriers from 

2

33 Fed. Reg. 17896 (Dec. 3, 1968). 

3

35 Fed. Reg. 16591 (Oct. 24, 1970).

4

73 Fed. Reg. 29550 (May 21, 2008).

5

Pub. L. No. 95-504, 92 Stat. 1705 (1978).

6

50 Fed. Reg. 52180 (Dec. 20, 1985). The 1986 allocation and withdrawal rules at the 

High Density Traffic Airports rules did not apply to Newark because the High Density Rule 

was not then in effect at that airport.
Appendix III: History of Slot Control Rules and 

Related Actions

Page 68 GAO-12-902 Airport Slot Controls

hoarding slots in an attempt to restrict service to drive up fares or keep 

smaller competitors from entering into or expanding in certain markets.” 

In the 1990s, we,7 Transportation Research Board,8 Department of 

Transportation (DOT)9

, and new entrant carriers, respectively, studied the 

High Density Rule and presented reports and congressional testimony 

that the High Density Rule was a barrier to competition and to improved 

service, in part because new airlines were unable to establish service at 

the slot-controlled airports because of the lack of slot availability.10

Subsequently, in April 2000, Congress required that the application of the 

High Density Rule be phased out at JFK and LaGuardia airports by 

January 1, 2007, and directed DOT, in the interim to grant exemptions to 

the High Density Rule to allow for a certain number of flights operated by 

new entrant airlines and flights serving small hub and nonhub airports if 

the aircraft had fewer than 71 seats.11 By the fall of 2000, DOT had 

granted the exemptions required by statute, and airlines had added 300 

scheduled flights at LaGuardia, resulting in a 144 percent increase in the 

average minutes of delay for arriving flights, from 15.52 minutes in March 

2000 (a month before the law was enacted) to 37.86 minutes in 

September 2000. Furthermore, FAA reported that by September 2000, 

flight delays at LaGuardia accounted for 25 percent of the nation’s delays, 

compared with 10 percent during the previous year. To address 

congestion at LaGuardia, FAA reduced the number of daily slot 

exemptions and distributed the exemptions through a lottery.12

 

7

GAO, Airline Competition: Industry Operating and Marketing Practices Limit Market 

Entry, GAO/RCED-90-147 (Washington, D.C.: Aug. 29, 1990). 

8

National Research Council Transportation Research Board, Entry and Competition in the 

U.S. Airline Industry: Issues and Opportunities, Special Report 255 (Washington, D.C.:

1999).

9

Department of Transportation, Study of the High Density Rule: Report to Congress

(Washington, D.C.: May 1995).

10See, e.g., H. R. Rep. No. 106-67, at 77 (1999). 

11Wendell H. Ford Aviation Investment and Reform Act for the 21st Century (AIR-21), Pub. 

L. No. 106- 181, 114 Stat. 61, 108-109 (Apr. 5, 2000). AIR-21 also required the phase-out 

of the application of the High Density Rule at O’Hare by July 1, 2002. 

1266 Fed. Reg. 48157 (2001).
Appendix III: History of Slot Control Rules and 

Related Actions

Page 69 GAO-12-902 Airport Slot Controls

In 2006, FAA proposed a congestion management rule for LaGuardia that 

would have replaced the High Density Rule when it expired on January 1, 

2007.13 The proposed rule would have encouraged the use of larger 

aircraft by implementing an average aircraft size requirement (with 

proposed exemptions for service to small communities). However, 

because FAA did not expect to complete the congestion management 

rule before the High Density Rule expired, the agency imposed temporary 

slot controls at LaGuardia effective on January 1, 2007 (a maximum of 75 

slots per hour) and required airlines to use slots at least 80 percent of the 

time.14 In addition, in 2007, the New York Aviation Rulemaking 

Committee15

After JFK and Newark airports experienced flight delays during the 

summer of 2007, in October 2007, FAA announced operational targets of 

81 flights per hour from 3:00 p.m. to 7:59 p.m. at JFK. In March 2008, by 

order, FAA imposed temporary slot controls at JFK (a maximum of 81 

slots per hour)

explored ways to reduce congestion and efficiently allocate 

scare capacity at the New York City area airports, including making 

operational and infrastructure improvements; using congestion pricing or 

auctions; requiring airlines to use larger aircraft; modifying gate 

allocations; amending or eliminating the perimeter rule; implementing 

priority aviation traffic preferences; or following International Air Transport 

Association’s Worldwide Slot Guidelines.

16 and in June 2008, by order, imposed temporary slot 

controls at Newark (a maximum of 81 slots per hour)17 and required 

airlines at those airports to use slots at least 80 percent of the time.18

 

1371 Fed. Reg. 51360 (Aug. 29, 2006).

Since 2008, FAA has extended the duration of the orders imposing slot 

controls at JFK, LaGuardia, and Newark; they are now in effect until 

October 2013 or until DOT’s Office of the Secretary and FAA issue a 

1471 Fed. Reg. 77854 (Dec. 27, 2006).

15Committee members included officials from DOT’s Office of the Secretary and FAA, the 

Port Authority of New York and New Jersey, and the State of New York as well as 

representatives from airlines and consumer groups. 

1673 Fed. Reg. 3510 (Jan. 18, 2008).

1773 Fed. Reg. 29550 (May 21, 2008).

1873 Fed. Reg. 3510 (Jan. 18, 2008); 73 Fed. Reg. 29550 (May 21, 2008).
Appendix III: History of Slot Control Rules and 

Related Actions

Page 70 GAO-12-902 Airport Slot Controls

congestion management rule.

19 In April 2008, FAA proposed that the 

congestion management rule for LaGuardia include two different options 

for auctioning new or returned slots at LaGuardia whereby under one 

option, the agency would have kept the proceeds and under the second 

option, the proceeds would have gone to the incumbent carrier holding 

the slot.20 In May 2008, FAA proposed applying such congestion 

management rules to JFK and Newark.21 In October 2008, FAA published 

final congestion management rules for JFK, LaGuardia, and Newark 

assigning to existing operators the majority of slots at the airports and 

creating a market by annually auctioning off a limited number of slots in 

each of the first 5 years of the 10-year rule.22 Before going into effect, on 

October 9, 2009, FAA rescinded23 the final rules for the congestion 

management rules for JFK, LaGuardia, and Newark citing, among other 

things, that the rulemakings had been highly controversial, a court 

challenge, and a resulting December 2008 United States Court of 

Appeals for the District of Columbia Circuit ruling24 that put on hold the 

implementation of the congestion management rules and their slot 

auction provisions.25 In its rescission of the congestion management 

rules, FAA additionally cited fiscal year 2009 appropriations act 

legislation26

 

1974 Fed. Reg. 845 (Jan. 8, 2009); 74 Fed. Reg. 51648 (Oct. 7, 2009); 74 Fed. Reg. 

51650 (Oct. 7, 2009); 74 Fed. Reg. 51653 (Oct. 7, 2009); 76 Fed. Reg. 18616 (Apr. 4, 

2011); 76 Fed. Reg. 18618 (Apr. 4, 2011); and 76 Fed. Reg. 18620 (Apr. 4, 2011).

providing, among other things, a statutory prohibition on 

2073 Fed. Reg. 20846 (Apr. 17, 2008). 

2173 Fed. Reg. 29626 (May 21, 2008).

2273 Fed. Reg. 60544, 60574 (Oct. 19, 2008). 73 Fed. Reg. 60544 (Oct. 10, 2008).

2374 Fed. Reg. 52132 (Oct. 9, 2009); 74 Fed. Reg. 52134 (Oct. 9, 2009).

24See, Dec. 8, 2008 Order, Port Authority of N.Y. & N.J. v. FAA, No. 08-1329.

25In addition, in a legal opinion issued to multiple congressional requesters, we concluded 

that FAA lacked the authority to auction slots and therefore also lacked authority to retain 

and use auction proceeds. GAO Legal Opinion on Federal Aviation Administration—

Authority to Auction Airport Arrival and Departure Slots and to Retain and Use Auction 

Proceeds, B-316796 (Sept. 30, 2008). The United States Department of Justice, Office of 

Legal Counsel, opined that FAA “would not violate the [Anti-Deficiency Act] by issuing and 

implementing the slot auction regulation.” U.S. Dep’t of Justice, Office of Legal Counsel, 

Whether the Federal Aviation Administration’s Finalizing and Implementing of Slot Auction 

Regulation Would Violate the Anti-Deficiency Act (Oct. 7, 2008).

26Omnibus Appropriations Act, 2009, Pub. L. No. 111-8, 123 Stat. 524, 921 (2009)
Appendix III: History of Slot Control Rules and 

Related Actions

Page 71 GAO-12-902 Airport Slot Controls

using fiscal year 2009 funds to take any action regarding the auctioning of 

rights or permission to conduct airlines operations at U.S. commercial 

airports.27 Subsequent to the rescission of the slot auction rules, FAA 

sought a dismissal of the case that was granted on October 14, 2009.28

In 2010, DOT’s Office of the Secretary and FAA began drafting a “Slot 

Management and Transparency” rule for the New York City area 

airports.29

In 2009, Delta Air Lines and US Airways proposed trading slots that they 

held at LaGuardia and Reagan National, a trade that would allow Delta to 

establish a domestic hub at LaGuardia and US Airways to enhance its 

network at Reagan National. The airlines sought FAA’s permission 

because the transaction was considered a purchase of slots that, under 

the order limiting operations at LaGuardia, was not allowed. Under the 

proposal, Delta would transfer 42 slot pairs it held at Reagan National in 

exchange for 125 slot pairs at LaGuardia, among other provisions. DOT’s 

Office of the Secretary and FAA granted the waiver request with 

conditions to counteract a substantial increase in market concentration by 

the two airlines that would result at those airports and to provide an 

According to DOT, this rulemaking would replace the current 

temporary orders limiting scheduled aircraft operations at JFK, 

LaGuardia, and Newark with a more permanent rule to address 

congestion and delay while also promoting fair access and competition.

DOT’s rulemaking is also aimed at ensuring that congestion and delay 

are minimized by limiting scheduled and unscheduled aircraft operations.

Although the temporary orders prohibit the buying and selling of slots at 

the New York City area airports, according to DOT, the rulemaking would 

establish a secondary market for U.S. and foreign air carriers to buy, sell, 

trade, and lease slots at the three airports and “allow carriers serving or 

seeking to serve the New York area airports to exchange slots as their 

business models and strategic goals require.” Under DOT’s rulemaking 

schedule, the department was to provide the draft to the Office of 

Management and Budget for review by April 25, 2011, but as of July 

2012, that had not yet occurred. At present, the High Density Rule applies 

only to Reagan National.

 

2774 Fed. Reg. 52132 (Oct. 9, 2009); 74 Fed. Reg. 52134 (Oct. 9, 2009).

28See Oct. 14, 2009 Order, Port Authority of N.Y. & N.J. v. FAA, No 08-1329.

29Reagan National is not included in this rulemaking because it is covered under FAA’s 

High Density Rule regulations. 
Appendix III: History of Slot Control Rules and 

Related Actions

Page 72 GAO-12-902 Airport Slot Controls

opportunity for low cost airlines to compete, which required them to divest 

14 pairs of slots at Reagan National and 20 pairs of slots at LaGuardia to 

new entrant and limited incumbent airlines (those holding less than 5 

percent of slots at Reagan National and LaGuardia).30 However, Delta 

and US Airways decided not to proceed with the transaction under these 

conditions. In 2011, the two airlines reapplied for permission to exchange 

slots. Under the revised proposal, Delta would acquire 132 slot pairs (265 

slots) at LaGuardia from US Airways and US Airways would acquire 42 

slot pairs at LaGuardia from Delta, among other provisions. Delta would 

also pay US Airways $65 million. In their application, the two airlines said 

consumers would benefit from the transaction through, among other 

things, improved connectivity at LaGuardia and Reagan National and by 

using larger aircraft. DOT’s Office of the Secretary and FAA approved the 

transaction and granted the waiver request from the temporary order’s 

prohibition on purchasing slots, with conditions, citing expected consumer 

benefits and the increased presence of low cost airlines at LaGuardia and 

Reagan National since the previous application.31 The conditions required 

Delta and US Airways to divest to new entrants and limited incumbents 

fewer slots—8 slot pairs at Reagan National and 16 slot pairs at 

LaGuardia—than DOT’s Office of the Secretary and FAA had required 

when they approved the first application. DOT’s Office of the Secretary 

and FAA directed that the divested slots be sold through a bidding 

process, permitting Delta and US Airways to keep the proceeds. In 2011, 

Jet Blue purchased 8 slot pairs at LaGuardia for $32 million and 8 slot 

pairs at Reagan National for $40 million, and West Jet purchased 8 slot 

pairs at LaGuardia for $17.6 million.

Since the 1950s, the Port Authority of New York and New Jersey, which 

operates the New York City area airports, has had a rule limiting the 

distance of nonstop flights into and out of LaGuardia known as the 

perimeter rule. Until 1984, the perimeter rule was informal and prohibited 

nonstop flights into or out of LaGuardia to or from destinations more than 

2,000 miles from the airport. In 1984, the Port Authority formally instituted 

a 1,500-mile perimeter rule but exempted service to Denver, which is 

more than 1,600 miles from LaGuardia, and flights on Saturdays.

 

3075 Fed. Reg. 26322 (May 11, 2010).

3176 Fed. Reg. 63702 (Oct. 13, 2011). 

Perimeter Rules Subject 

Airlines to Flight Distance 

Limitations to and from 

Reagan National and 

LaGuardia
Appendix III: History of Slot Control Rules and 

Related Actions

Page 73 GAO-12-902 Airport Slot Controls

In 1966, airlines at Reagan National voluntarily agreed to limit nonstop 

flights from the airport to destinations less than 650 miles away, with 

some exceptions. The Metropolitan Washington Airports Authority Act of 

1986, enacted into law in October 1986, authorized the transfer of 

authority over Reagan National and Dulles from the federal government 

to the Metropolitan Washington Airports Authority, set Reagan National’s 

perimeter rule at 1,250 miles, and prohibited the Airports Authority from 

increasing slot limits at Reagan National set in FAA’s High Density Rule.32

Two federal laws respectively enacted in 2000 and 2003 (the Wendell H. 

Ford Aviation Investment and Reform Act for the 21st Century33 (AIR-21) 

and the Vision 100-Century of Aviation Reauthorization Act34 (Vision 

100)) enacted statutory modifications relating to the slot and perimeter 

rules at Reagan National. Among other things, AIR-21 required the 

Secretary of Transportation to grant 12 beyond perimeter and 12 within 

perimeter exemptions at Reagan National. Vision 100 amendments 

increased these numbers to 24 beyond perimeter exemptions and 20 

within perimeter exemptions.35 In effect, AIR-21 and Vision 100, 

combined, required the Secretary of Transportation to award 22 round 

trips, 12 with service to airports beyond the perimeter and 10 with service 

to airports within the perimeter.36 In 2012, the FAA Modernization and 

Reform Act of 201237

 

32Pub. L. No. 99-500, 100 Stat. 1783, 1783-375 (1986); Pub. L. No. 99-591, 100 Stat. 

3341, 3341-376 (1986).

was enacted into law, which reauthorized FAA, 

authorized 16 additional beyond perimeter exemptions at Reagan 

National comprised of eight within-perimeter flights to large hub airports to 

be converted to nonstop beyond-perimeter flights (four round-trips) and 

33Pub. L. No. 106-181, 114 Stat. 61 (2000).

34Pub. L. No. 108-176, 117 Stat. 2490 (2003).

35In addition, these two laws together mandated that the slot exemptions at Reagan 

National (1) could not be used for operations between the hours of 10:00 p.m. and 7:00 

a.m. and (2) could not increase the number of operations in any 1-hour period during the 

hours between 7:00 a.m. and 9:59 p.m. by more than 3 operations. 

36More specifically, these two laws together required the Secretary of Transportation to 

grant 24 beyond perimeter exemptions and 20 slot exemptions within the 1,250-mile 

perimeter.

37Pub. L. No. 112-95, 126 Stat. 11 (2012). In addition the FAA Modernization and Reform 

Act of 2012 amended the hourly limitations provision whereby such slot exemptions may 

not increase the number of operations in any 1-hour period during the hours between 7:00 

a.m. and 9:59 p.m. by more than 5 operations
Appendix III: History of Slot Control Rules and 

Related Actions

Page 74 GAO-12-902 Airport Slot Controls

eight new additional nonstop beyond-perimeter flights (four round trips).

With respect to the converted flights, under the 2012 act, each incumbent 

airline with 40 or more slots at Reagan National could convert one withinperimeter slot pair to one beyond-perimeter slot pair,38

 

38Four airlines each qualified to convert one slot pair.

while the new 

beyond-perimeter slots were to be awarded to new entrants or airlines 

holding fewer than 40 slots. As the converted nonstop beyond-perimeter 

destinations, the incumbent airlines chose Los Angeles (American 

Airlines); Salt Lake City (Delta Air Lines); San Diego (US Airways); and 

San Francisco (United Airlines). Seven airlines applied for the four new 

beyond-perimeter slot pair exemptions, which, on May 14, 2012, DOT 

awarded to Alaska Airlines for Portland, Ore.; Jet Blue for San Juan, 

Puerto Rico; Southwest Airlines for Austin, Tex.; and Virgin America for 

San Francisco.
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 75 GAO-12-902 Airport Slot Controls

Figures 8 through 31 below show the trends in average annual passenger 

traffic and airfares at Baltimore-Washington International Thurgood 

Marshall Airport (BWI) and Dulles International Airport (Dulles) for 

destinations granted beyond-perimeter slot exemptions at Reagan 

National Airport (Reagan National) under AIR-21 and Vision 100 between 

2000 and 2004.

Figure 8: Indexed Average Passenger Traffic for All BWI Domestic Flights and 

Flights between BWI and Denver International Airport, 2000 to 2011

Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 76 GAO-12-902 Airport Slot Controls

Figure 9: Indexed Average Annual Airfare for All BWI Domestic Flights and Flights 

between BWI and Denver International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 77 GAO-12-902 Airport Slot Controls

Figure 10: Indexed Average Annual Passenger Traffic for All BWI Domestic Flights 

and Flights between BWI and Las Vegas McCarran International Airport, 2000 to 

2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 78 GAO-12-902 Airport Slot Controls

Figure 11: Indexed Average Annual Airfares for All BWI Domestic Flights and 

Flights between BWI and Las Vegas McCarran International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 79 GAO-12-902 Airport Slot Controls

Figure 12: Indexed Average Passenger Traffic for All BWI Domestic Flights and 

Flights between BWI and Los Angeles International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 80 GAO-12-902 Airport Slot Controls

Figure 13: Indexed Average Annual Airfares for All BWI Domestic Flights and 

Flights between BWI and Los Angeles International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 81 GAO-12-902 Airport Slot Controls

Figure 14: Indexed Average Passenger Traffic for All BWI Domestic Flights and 

Flights between BWI and Phoenix Sky Harbor International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 82 GAO-12-902 Airport Slot Controls

Figure 15: Indexed Average Airfares for All BWI Domestic Flights and Flights 

between BWI and Phoenix Sky Harbor International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 83 GAO-12-902 Airport Slot Controls

Figure 16: Indexed Average Passenger Traffic for All BWI Domestic Flights and 

Flights between BWI and Salt Lake City International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 84 GAO-12-902 Airport Slot Controls

Figure 17: Indexed Average Airfares for All BWI Domestic Flights and Flights 

between BWI and Salt Lake City International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 85 GAO-12-902 Airport Slot Controls

Figure 18: Indexed Average Passenger Traffic for All BWI Domestic Flights and 

Flights between BWI and Seattle-Tacoma International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 86 GAO-12-902 Airport Slot Controls

Figure 19: Indexed Average Airfares for All BWI Domestic Flights and Flights 

between BWI and Seattle-Tacoma International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 87 GAO-12-902 Airport Slot Controls

Figure 20: Indexed Average Passenger Traffic for All Dulles Domestic Flights and 

Flights between Dulles and Denver International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 88 GAO-12-902 Airport Slot Controls

Figure 21: Indexed Average Airfares for All Dulles Domestic Flights and Flights 

between Dulles and Denver International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 89 GAO-12-902 Airport Slot Controls

Figure 22: Indexed Average Annual Passenger Traffic for All Dulles Domestic 

Flights and Flights between Dulles and Las Vegas McCarran International Airport, 

2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 90 GAO-12-902 Airport Slot Controls

Figure 23: Indexed Average Annual Airfares for All Dulles Domestic Flights and 

Flights between Dulles and Las Vegas McCarran International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 91 GAO-12-902 Airport Slot Controls

Figure 24: Indexed Average Annual Passenger Traffic for All Dulles Domestic 

Flights and Flights between Dulles and Los Angeles International Airport, 2000 to 

2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 92 GAO-12-902 Airport Slot Controls

Figure 25: Indexed Average Annual Airfares for All Dulles Domestic Flights and 

Flights between Dulles and Los Angeles International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 93 GAO-12-902 Airport Slot Controls

Figure 26: Indexed Average Annual Passenger Traffic for All Dulles Domestic 

Flights and Flights between Dulles and Phoenix Sky Harbor International Airport, 

2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 94 GAO-12-902 Airport Slot Controls

Figure 27: Indexed Average Annual Airfares for All Dulles Domestic Flights and 

Flights between Dulles and Phoenix Sky Harbor International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 95 GAO-12-902 Airport Slot Controls

Figure 28: Indexed Average Annual Passenger Traffic for All Dulles Domestic 

Flights and Flights between Dulles and Salt Lake City International Airport, 2000 to 

2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 96 GAO-12-902 Airport Slot Controls

Figure 29: Indexed Average Airfares for All Dulles Domestic Flights and Flights 

between Dulles and Salt Lake City International Airport, 2000 to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 97 GAO-12-902 Airport Slot Controls

Figure 30: Indexed Average Annual Passenger Traffic for All Dulles Domestic 

Flights and Flights between Dulles and Seattle-Tacoma International Airport, 2000 

to 2011
Appendix IV: Trends in Average Annual 

Passenger Traffic and Airfares at Selected 

Washington, D.C., Area Airports

Page 98 GAO-12-902 Airport Slot Controls

Figure 31: Indexed Average Annual Airfares for All Dulles Domestic Flights and 

Flights between Dulles and Seattle-Tacoma International Airport, 2000 to 2011
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 99 GAO-12-902 Airport Slot Controls

The regression analysis explained in this appendix is designed to assess 

whether airlines tend to use smaller aircraft on flights to or from slotcontrolled airports. The analysis is based on data for all scheduled 

passenger airline flights between large hub domestic airports for two 

different Thursdays (one in winter and one in summer) in 2011, and 

assesses whether and how several factors—including whether the flight is 

scheduled to arrive or depart a slot-controlled airport—are correlated with 

the use of smaller aircraft. For the base-case analysis we defined a 

smaller aircraft as ones with 100 seats or fewer. Specifically, this 

appendix discusses (1) the model hypothesis, (2) the conceptual 

framework of the model, (3) data source and variable definitions, and (4) 

base-case model results and sensitivity analyses.

As discussed in the report, a variety of parties—airlines, the Port Authority 

of New York and New Jersey, and Department of Justice—assert that 

airlines currently operating out of slot-controlled airports use some of their 

slots in ways to keep out their competitors. One of these ways is using 

smaller aircraft, on average, at the four slot-controlled airports in an effort 

to meet the 80 percent usage rule.

As discussed in our report, we examined the number and proportion of 

scheduled passenger flights using smaller aircraft departing or arriving 

slot-controlled airports (which includes four airports) and the remaining 24 

large hub airports.1

Many factors may contribute to an airline’s decision to use smaller 

aircraft, such as location and proximity to other major markets, restrictions 

on distance flown, the type of passengers being served, and the airline’s 

route structure (e.g., a hub-and-spoke structure verses point-to-point). For 

example, all four of the slot-controlled airports are on the Eastern 

In comparing flights arriving and departing the slotcontrolled airports with other large hub airports that are not slotcontrolled, we found that the four slot-controlled airports had a higher 

proportion of scheduled flights with smaller aircraft than flights to or from 

the remaining 24 large hub airports. We found that these differences are 

statistically significant.

 

1

We included all large hub airports in the United States identified by FAA for calendar year 

2010 (the most recent year available for this list), excluding Honolulu International.

Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Model Hypothesis

Conceptual Framework of 

Model
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 100 GAO-12-902 Airport Slot Controls

Seaboard of the United States with many destinations—large and small—

within reasonably close proximity. Because shorter distance flights are 

generally served by smaller aircraft, flights to and from the slot-controlled 

airports may have a higher proportion of flights with small aircraft. Also, 

LaGuardia and Reagan National are subject to perimeter rules of 1,500 

and 1,250 miles, respectively, that limits the distance of flights from these 

airports. A restriction on flight distance such as this would likely skew 

aircraft use toward smaller sized craft. Whether an airport being served is 

a business versus leisure (tourist) market may also affect the size of 

aircraft—for example, flights serving leisure markets may tend to use 

larger aircraft less frequently than a business market. And finally, an 

airline’s route structure could influence the distance of flights or aircraft 

size—for example, an airport that serves as a hub for an airline will 

require more short distance flights than a point-to-point business model.

Since a variety of factors in addition to slot controls may be correlated 

with the use of a small aircraft, we developed a logistic regression model 

that controls for other factors that may be correlated with aircraft size. To 

isolate the correlation between flights arriving or departing slot-controlled 

airports and aircraft size, we defined aircraft as small if its capacity was 

100 seats or fewer.2 We applied a logistic regression technique (or logit 

model) in which the scheduled flights are defined as using small aircraft 

(100 seats or fewer) or large (more than 100 seats), and assessed how 

each of a set of independent factors (including whether the flights arrives 

or departs a slot-controlled airport) correlates with the odds of a small 

aircraft used on that flight. All factors related to aircraft size may not be 

fully controlled for by this model. Also, as with any regression model, this 

analysis does not prove a causal relationship between aircraft size and 

slot-controlled airport, only the correlation between the two.

The primary data source for the model is airlines’ schedule data from 

Innovata, which provides information on all airlines scheduled flights. The 

level of observation for this analysis is each individually scheduled 

 

2

One hundred seats is generally the maximum seat capacity of most regional jet aircraft.

See below for a discussion of alterative cutoffs for the definition of a small aircraft. 

Data Source and Variables
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 101 GAO-12-902 Airport Slot Controls

passenger flight. We used all flights between the 28 large hub airports3

The dependent variable for the analysis is a dummy (or indicator) 

variable—that is, a variable that takes a value of one or zero depending 

on the presence or absence of some characteristic. In this case, the 

dependent variable takes the value of one if the scheduled flight uses a 

small aircraft size (100 or fewer seats) and the value of zero if the flight 

uses a large aircraft (greater than 100 seats).

on 

two Thursdays in 2011—February 10, 2011, and August 11, 2011—for a 

total of 13,901 flights. Thursdays are generally considered to be a highdemand day, and February and August are representative months for the 

winter and summer seasons, respectively. The schedule data provide 

relevant information for each flight, including the size of aircraft, the date 

and time of the scheduled flight, the origin and destination airport, and the 

marketing and operating airline.

Slot-controlled airport (variable of interest): A dummy variable that 

takes the value of one if either the origin or destination of the flight is a 

slot-controlled airport. We used several different slot-controlled airport 

dummy variables, including one for all four slot-controlled airports as a 

group (slot4), one for only the three New York City area slot-controlled 

airports (slot3) and one for each individual slot-controlled airport alone.

Legacy airline: A dummy variable that takes the value of one if the flight

is marketed by one of the legacy airlines we defined (Delta Air Lines, 

United Airlines, American Airlines, US Airways, and Continental Airlines) 

and takes the value of zero for all other marketing airlines. Airlines vary in 

their fleet mix. Some airlines—either on their own or through partnerships 

 

3

The large hub airports included in our analysis are: Atlanta Hartsfield International, 

Boston Logan International, Baltimore-Washington International, Charlotte/Douglas 

International, Reagan National, Denver International, Dallas-Fort Worth International, 

Detroit Metro Wayne County, Newark, Fort Lauderdale-Hollywood International, 

Washington Dulles International, George Bush Intercontinental, JFK, Las Vegas McCarran 

International, Los Angeles International, LaGuardia, Orlando International, Chicago 

Midway, Miami International, Minneapolis-St. Paul International, Chicago O’Hare 

International, Philadelphia International, Phoenix Sky Harbor International, San Diego 

International Lindbergh, Seattle-Tacoma International, San Francisco International, Salt 

Lake City International, and Tampa International. 

4

In addition to the independent variables listed here, we tested whether scheduled flights 

in February (winter) had any greater likelihood of using a small aircraft than scheduled 

flights in August (summer). We did not find any significant difference, so we did not 

include this variable in our analysis. 

Dependent Variable

Independent Variables4
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 102 GAO-12-902 Airport Slot Controls

with other airlines—operate a varied fleet mix with both large and small 

aircraft, while other airlines tend to fly only a few aircraft types that may 

have little variation in the size of aircraft. We expect that when the 

marketing airline is a legacy airline, all else equal, there is a greater 

propensity to use smaller aircraft because these airlines and their 

partners tend to deploy a wide range of aircraft size, including many 

commuter-sized aircraft, across a broad range of types of routes.

Flight distance: A categorical variable that is derived from distance 

quartiles of the flights analyzed. The four distance categories are less 

than 325 miles, 325 to 602 miles, 603 to 998 miles, and greater than 998 

miles. Flight distance is a key factor in the decision underlying the 

assignment of aircraft to flights. We used the flights that fell into the 

second quartile (325 miles to 602 miles in distance) as the reference 

category that the other flight distance dummy variables are compared to. 

We expect that shorter flights would tend to use smaller aircraft.

Flight frequency for an airline route: A categorical variable indicating 

the importance of a particular route to an airline’s operations. We define 

flight frequency on an airline’s route as the total number of flights 

operated by the same airline on a given day from the same origin to the 

same destination. Few frequencies on an airline’s route indicate that the 

route may not be highly connected to the airline’s network, while 

numerous frequencies indicate a greater degree of connection, possibly 

involving one of the airline’s hub airports.5

Tourism: A dummy variable that takes the value of one if either the origin 

or destination of a flight is one of three cities that have substantial tourist 

travel (Las Vegas, Nevada; Orlando, Florida; and Fort Lauderdale, 

Florida) based on hotel revenues relative to population and our judgment 

We divided the number of 

flights on an airline’s route into quartiles and used the two lower quartiles 

(which together included all airlines’ routes with fewer than 6 flights per 

day) as reference categories that the remaining two quartiles are 

compared to. The third quartile includes airlines’ routes with 6 to 8 flights 

and day and the fourth quartile includes routes with 9 or more flights per 

day. We expect that greater dedication to serving a route (higher flight 

frequency) will be correlated with reduced odds of using a small aircraft.

 

5

Flight frequency also serves as a proxy for an airport hub variable that would consider 

whether the airport serves as a network hub for an airline. 
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 103 GAO-12-902 Airport Slot Controls

about which cities have substantial tourist travel. We defined Las Vegas 

McCarran International, Orlando International, and Fort LauderdaleHollywood International airports as the three tourism-oriented airports in 

the analysis. We expect that smaller aircraft will be less likely to be used 

on flights to and from these airports.

Table 7 provides results of our base-case model that defines a small 

aircraft as one with 100 seats or fewer. The results are expressed as 

odds ratios, which represents the odds that a flight uses a small aircraft 

(100 seats or fewer) divided by the odds that a flight uses a large aircraft 

(more than 100 seats). The odds ratio for the variable of interest (slot4) is 

greater than 1, indicating that a flight to or from any of the four slotcontrolled airports is more likely to use a small aircraft than a flight to or 

from the other 24 large hub airports that are not slot-controlled.6

 

6

Odds are a ratio of the probability that an event will occur versus the probability that the 

event will not occur, or probability / (1-probability). Odds ratios, therefore, are simply a

ratio of odds; in general they refer to the ratio of the odds of an event (small aircraft) 

occurring in the exposed group (slot-controlled airports) versus the unexposed group 

(other large hubs). 

Specifically, the odds that a flight to or from a slot-controlled airport uses 

a smaller aircraft is 75 percent higher than the odds for a flight to and 

from the other 24 large hub airports that are not slot-controlled. This result 

and the odds ratios for all other variable in the base-case scenario are 

statistically significant.

Base-Case Model Results 

and Sensitivity Analysis
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 104 GAO-12-902 Airport Slot Controls

Table 7: Logistic Regression Results for Slot-Controlled-Airport and Aircraft-Size 

Model, Small Aircraft with 100 Seats or Fewer

Variable Odds ratio

To or from any of the four slot-controlled airports

a

1.75

To or from tourism airport 0.16

Marketed by a legacy airline 8.71

6 to 8 flights per day by same airline from same origin to same destination 0.32

9 or more flights per day by same airline from same origin to same 

destination

0.11

Flight distance less than 325 miles 3.99

Flight distance between 603 and 998 miles 0.40

Flight distance more than 998 miles 0.06

Source: GAO analysis of airline schedule data

a

All odds ratios are significant at the p-value <0.01 (1 percent level). The significance of the 

coefficients in the models was evaluated using a simple Wald test statistic, which is asymptotically 

equivalent to the likelihood-ratio chi-square statistic. The percentage of flights correctly predicted by 

the model to be on small versus larger aircraft was 85-percent. The measure is known as the 

concordance rate. 

In addition to the model discussed above, we also ran with the model with 

alternative definitions of the slot-controlled-airport dummy variable. Table 

8 shows the odds ratios from these 5 addition model runs for the variously 

defined slot-controlled-airport variable. The results for the independent 

variables in these model runs were reasonably stable both in the direction 

and magnitude of the odds ratios.

Table 8: Logistic Regression Results for Alternative Slot-Controlled-Airport Variable 

Definitions, Small Aircraft with 100 Seats or Fewer

Slot-controlled-airport variable Odds Ratio

To or from any of the three New York City area slot-controlled airports 1.68

To or from LaGuardia

a

2.08

To or from JFK

a

1.63

To or from Newark

a

1.22

To or from Reagan National

b

1.72

Source: GAO analysis of airline schedule data

a

a

Indicates odds ratio is significant at a p-value > 0.01. 

b

Indicates odds ratio is significant at a p-value < 0.1. 

We also conducted sensitivity analyses by testing two alternative 

definitions for small aircraft. We ran the same models described above, 
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size 

Page 105 GAO-12-902 Airport Slot Controls

but defined a small aircraft as (1) aircraft with 124 seats or fewer (which is 

the median aircraft size for this data set) and (2) aircraft with 80 seats or 

fewer (which excludes the largest regional jets). Tables 9 and 10 show 

the results of these model runs, including the results for each of the six 

different slot-controlled airport dummy variable definitions. All other 

independent variables included in the models were robust—both in terms 

of the direction, magnitude, and statistical significance of odds ratios—

across the three definitions for small aircraft.

In addition, the odds ratios for all definitions of the slot-controlled-airport 

dummy variable are greater than 1—indicating a greater odds of a flight 

using a small aircraft to or from the slot-controlled airport, however the 

slot variable was defined. The magnitude of the odds ratio, however, 

varies based on the definition of a small aircraft (that is, a cutoff of 80, 

100, or 124 seats). Also, the degree of the statistical significance of the 

odds ratios for Newark and JFK vary. The odds ratio for Newark becomes 

more significant under the alternative aircraft definitions (i.e., a cutoff of 

80 or 124 seats). And, while odds ratio for the JFK dummy variable was 

significant in both the base case (100-seat cutoff) and the 124-seat cutoff, 

the odds ratio for JFK is not statistically significant in the 80 seat cutoff.

Table 9: Logistic Regression Results for Alternative Slot-Controlled-Airport Variable 

Definitions, Small Aircraft with 124 Seats or Fewer

Slot-controlled airport variable Odds Ratio

To or from any of the four slot-controlled airports 2.49

To or from any of the three New York City area slot-controlled airports

a

2.18

To or from LaGuardia

a

3.68

To or from JFK

a

1.53

To or from Newark

a

1.48

To or from Reagan National

a

4.29

Source: GAO analysis of airline schedule data

a

a

Indicates odds ratio is significant at p-value < 0.01. 
Appendix V: Logistic Regression Analysis of 

Slot-Controlled Airports and Aircraft Size

Page 106 GAO-12-902 Airport Slot Controls

Table 10: Logistic Regression Results for Alternative Slot-Controlled-Airport 

Variable Definitions, Small Aircraft with 80 Seats or Fewer

Slot-controlled airport variable Odds Ratio

To or from any of the four slot-controlled airports 1.55

To or from any of the three New York City area slot-controlled airports

a

1.61

To or from LaGuardia

a

2.17

To or from JFK

a

1.22

To or from Newark 1.26

To or from Reagan National

b

1.41

Source: GAO analysis of airline schedule data

a

a

Indicates odds ratio is significant at p-value < 0.01. 

b

Indicates odds ratio is significant at p-value < 0.05. 
Appendix VI: Comments from the Metropolitan 

Washington Airports Authority

Page 107 GAO-12-902 Airport Slot Controls

Appendix VI: Comments from the 

Metropolitan Washington Airports Authority
Appendix VI: Comments from the Metropolitan 

Washington Airports Authority

Page 108 GAO-12-902 Airport Slot Controls
Appendix VI: Comments from the Metropolitan 

Washington Airports Authority

Page 109 GAO-12-902 Airport Slot Controls
Appendix VI: Comments from the Metropolitan 

Washington Airports Authority

Page 110 GAO-12-902 Airport Slot Controls
Appendix VII: Comments from the Port 

Authority of New York and New Jersey 

Page 111 GAO-12-902 Airport Slot Controls

Appendix VII: Comments from the Port 

Authority of New York and New Jersey
Appendix VIII: GAO Contact and Staff 

Acknowledgments

Page 112 GAO-12-902 Airport Slot Controls

Susan Fleming (202) 512-2834 or flemings@gao.gov

In addition to the individual named above, Amy Abramowitz, Paul 

Aussendorf, Geoff Hamilton, Bob Homan, David Hooper, Delwen Jones, 

Kirsten Lauber, Josh Ormond, Dae Park, and Gretchen Snoey made 

significant contributions to this report.

Appendix VIII: GAO Contact and Staff 

Acknowledgments 

GAO Contact

Staff 

Acknowledgments

(541086)
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