Reagan National Airport: Update on Capacity to Handle Additional Flights and Impact on Other Area Airports
Published: 2007-02-28T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: In 1999, GAO reported that Reagan National Airport could accommodate at least 36 more slots, which are authorizations from the Department of Transportation (DOT) for a takeoff or landing. In 2000 and 2003, two federal statutes, known as AIR-21 and Vision 100, permitted DOT to award 44 new slots to airlines, 24 of which could be used for flights to cities more than 1,250 miles, which was the statutorily mandated limit for non stop flights from Reagan National. The DOT awards went to airlines serving six cities (Denver, Las Vegas, Los Angeles, Phoenix, Salt Lake City, and Seattle). For this year's reauthorization of the Federal Aviation Administration (FAA), GAO was asked for an update on the capacity of Reagan National to accommodate additional slots and the effect of relaxing the perimeter rule. GAO updated its 1999 study to answer these key questions: (1) To what extent can Reagan National accommodate additional flights? (2) Since AIR-21 and Vision 100, what changes have occurred in market share and fares for flights operating between the six beyond-perimeter cities and the three Washington, D.C., area airports? In commenting on this report, DOT and the airports authority generally agree with our findings but with one exception, the airports authority disagrees with DOT's estimate of slots because it disputes their methodological assumptions. We believe the department's methodology for estimating airport capacity is appropriate.
section_title: What GAO Found
paragraphs: Reagan National Airport can accommodate some additional in capacity, but airport infrastructure constrains how much can be added. FAA officials believe that some additional slots can be added, while airport officials have not made an estimate. FAA, using the results of a 1995 DOT capacity study, determined that the airport's airside infrastructure (e.g., runways) could accommodate four additional slots per hour. Airport officials said they were unsure how many additional slots, if any, the airport could accommodate but cited several factors that could limit the airport's capacity to absorb additional slots including the limited number of gates currently available for loading airplanes and other infrastructure constraints. GAO's work shows that even if the number of slots is not increased, there is some opportunity to expand current capacity by filling unused slots and increasing the size of aircraft on existing slots to increase the number of flights and the number of passengers served. Currently, nearly 80 slots are unused because they are at early morning or late evening times and airlines have not applied to use these time slots. In addition, many of the slots reserved for large passenger jets are currently being used by smaller regional jets. Airlines awarded slots for direct flights between Reagan National and the six beyond-perimeter cities gained significant market share in those selected cities, but the effect of these slots on competing flights operating between these cities and the other Washington, D.C. area airports is not evident. For each of the six beyond-perimeter cities, the direct flights to and from Reagan National captured the majority of passengers flying between that city and Reagan National. In most cases, the airlines charged higher fares than competing connecting flights. GAO did not find evidence in passengers or fare data that would indicate that the new service between Reagan National and the six beyond perimeter cities had substantially affected service from Dulles or Baltimore-Washington International airports to these cities.

section_title: Letter
paragraphs: Ronald Reagan Washington National Airport’s (Reagan National) central  Ronald Reagan Washington National Airport’s (Reagan National) central  location in the Baltimore-Washington D.C.–Northern Virginia region and  location in the Baltimore-Washington D.C.–Northern Virginia region and  proximity to the Nation’s capital makes it very popular for airlines and  proximity to the Nation’s capital makes it very popular for airlines and  passengers. However, since the 1960’s, the federal government has  passengers. However, since the 1960’s, the federal government has  restricted air traffic at Reagan National to reduce congestion and spur  restricted air traffic at Reagan National to reduce congestion and spur  growth at other nearby airports. This has been achieved by controlling the  growth at other nearby airports. This has been achieved by controlling the  number of takeoffs and landings that can occur at Reagan National each  number of takeoffs and landings that can occur at Reagan National each  day within hourly time periods. To take off or land during any given hour  day within hourly time periods. To take off or land during any given hour  at Reagan National, an airline must first obtain a slot that is an  at Reagan National, an airline must first obtain a slot that is an  authorization from the Federal Aviation Administration (FAA) under what  authorization from the Federal Aviation Administration (FAA) under what  is called the slot rule. Each slot equates to one takeoff or landing. The  is called the slot rule. Each slot equates to one takeoff or landing. The  airport’s growth has also been constrained by limiting the distance that  airport’s growth has also been constrained by limiting the distance that  flights are allowed to travel. Under what is called the perimeter rule, the  flights are allowed to travel. Under what is called the perimeter rule, the  distance of nonstop flights that serve the airport is limited to 1,250 miles.  distance of nonstop flights that serve the airport is limited to 1,250 miles.  Under this rule, passengers wishing to fly to Reagan National from airports  Under this rule, passengers wishing to fly to Reagan National from airports  more than 1,250 miles away must first fly to an airport within 1,250 miles  more than 1,250 miles away must first fly to an airport within 1,250 miles  and then take another flight continuing on to Reagan National. The slot  and then take another flight continuing on to Reagan National. The slot  rule also grants 12 slots per hour to general aviation or other aircraft that  rule also grants 12 slots per hour to general aviation or other aircraft that  do not operate on a scheduled basis, such as corporate jets or military  do not operate on a scheduled basis, such as corporate jets or military  planes. Prior to the terrorist attacks of September 11, 2001, there were  planes. Prior to the terrorist attacks of September 11, 2001, there were  over 40,000 annual general aviation and unscheduled flights to and from  over 40,000 annual general aviation and unscheduled flights to and from  Reagan National but since then, the Department of Homeland Security  Reagan National but since then, the Department of Homeland Security  (DHS) restrictions on general aviation flights in the national capital region  (DHS) restrictions on general aviation flights in the national capital region  have drastically curtailed the use of these slots to about 200 over the past  have drastically curtailed the use of these slots to about 200 over the past  year.  year.
In 1999, we analyzed legislative proposals to increase the number of slots  In 1999, we analyzed legislative proposals to increase the number of slots  at Reagan National and reported that the airport could accommodate at  at Reagan National and reported that the airport could accommodate at  least 36 more slots per day and that adding beyond-perimeter slots would  have limited effects on nearby Dulles International (Dulles) and Baltimore- Washington Thurgood Marshall International Airport (BWI). The rule that  governs the number of slots at Reagan National limits the number of  takeoffs or landings to 48 commercial slots per hour occurs during an 18- hour period (6:00 a.m. to midnight) over the airport’s 24-hour operating  day.
In 2000 and 2003, two federal statutes —AIR-21 and Vision 100 increased  the number of slots and for the first time allowed for exemptions to be  granted to the perimeter rule. The statutes granted exemptions to the  existing rules, adding 44 slots per day during a 15-hour period and allowing  24 of these slots for flights of more than 1,250 miles—flights longer than  1,250 miles are called beyond-perimeter flights. In effect, given the 15- hour period for these slot exemptions, this added on average three  commercial slots per hour. The Department of Transportation (DOT)  awarded these new slots exemptions to airlines and routes that best met  specified criteria. The 24 beyond-perimeter slot exemptions were  awarded to airlines operating flights from six airports–Denver  International (Denver), Phoenix-Sky Harbor (Phoenix), McCarran  International (Las Vegas), Los Angeles International (Los Angeles), Salt  Lake City International (Salt Lake City), and Seattle-Tacoma International  (Seattle).
In anticipation of this year’s reauthorization of FAA, you asked for an  update of GAO’s 1999 report on Reagan National’s ability to accommodate  additional capacity and the effect of relaxing the perimeter rule. To  provide this update, we addressed these key questions:    To what extent can Reagan National accommodate additional flights?
Since AIR-21 and Vision 100, for the six beyond-perimeter airports, what  changes have occurred in market share and fares at Reagan National and  what changes have occurred in the number of passengers and fares at  Dulles and BWI airports?
To identify the number of additional slots Reagan National can  accommodate and the factors affecting existing capacity, we reviewed  FAA flight data and gate utilization data obtained from the Metropolitan  Washington Airports Authority (airports authority) and we interviewed  DOT, FAA and airport officials. To assess the changes in passenger levels  and fares at Washington area airports and the six beyond-perimeter  airports, we analyzed DOT origin and destination ticket data and  interviewed officials at all three Washington, D.C., area airports. We  reviewed the reliability of these data and concluded that they were  sufficiently reliable for our purposes. We conducted our work from July  2006 to February 2007 in accordance with generally accepted government  auditing standards. More details about the scope and the methodology of  our work are presented in appendix I.
subsections: section_title: Background
paragraphs: Reagan National Airport was built by the federal government and opened  on June 16, 1941, on the western bank of the Potomac River, across from  Washington, D.C. Reagan National currently has three runways and two  terminals with a total of 44 gates or passenger loading ramps for use by air  carriers. The airport currently handles 400 daily departures to 75 cities,  offered by 20 different airlines (this includes commuter airlines, which  operate solely for the major carriers). Terminal A, the original terminal,  has 9 gates, and Terminal B/C, which opened in 1997, has 35 gates, 100  ticket counters, and 12 baggage claim areas. In 2005, 17.8 million  passengers used Reagan National. The airline with the largest number of  flights at Reagan National is US Airways, which controls 44 percent of the  commercial slots. The next largest operators are Delta Airlines and  American Airlines, which have 14 percent of the commercial slots each.  During 2005, these three airlines together accounted for nearly 60 percent  of total passenger enplanements at the airport.
In 1969, FAA applied special air traffic rules to certain airports facing  increasing delays and congestion that it designated as high-density  airports: Chicago-O’Hare; New York’s LaGuardia and Kennedy; Newark,  New Jersey; and Reagan National (DOT dropped Newark’s designation as  a high-density airport in October 1970). Because of the restricted number  of allowable flights, these airports are generally known as slot-controlled,  and the special air traffic rules governing the allowable number of flights  are referred to as slot rules, or high-density rules.
The number of hourly slots at Reagan National is controlled by the federal  government. Since 1969, the federal government has restricted the number  of commercial takeoffs and landings at Reagan National. Currently, the  number allowed is 48 per hour: 37 for air carriers and 11 for commuter  aircraft. Table 1 shows the number of slots per hour by type of aircraft  permitted under the slot rule. FAA authorizes general aviation or  unscheduled aircraft to make an additional 12 takeoffs or landings during  each hour for a total of 60 slots per hour.
A perimeter rule has been in place at Reagan National since May 1966  restricting airlines from operating nonstop flights between Reagan  National and airports further than a specified distance. The FAA  previously had concerns that allowing long-range jets to fly into Reagan  National would create a noise problem and hamper growth of the newly  built Dulles International Airport. As a result, with the airlines agreeing,  the Civil Aeronautics Board approved a 650-mile perimeter, with  exceptions of seven cities between 650 and 1,000 miles away that enjoyed  grandfather status as of December 1, 1965.
In 1986, the Congress codified the slot and perimeter rules into federal  statute as part of the Metropolitan Washington Airports Act of 1986. The  act led to the transfer of authority over Reagan National and Dulles from  the federal government to the Metropolitan Washington Airports Authority  and set the perimeter at 1,250 miles, which allowed nonstop flights as far  as Houston and Dallas.
Two federal statutes enacted in 2000 and 2003 modified the slot and  perimeter rules at Reagan National Airport. AIR-21 and Vision 100  effectively added up to three commercial slots per hour and for the first  time designated some slots for flights beyond the 1,250 mile perimeter.  AIR-21 and Vision 100, combined, allowed the Secretary of Transportation  to award 22 roundtrips, 12 with service to airports beyond the perimeter  and 10 with service to airports within the perimeter. Figure 2 shows each  market by number of slots and airline.
Two other commercial airports serve the Baltimore-Washington  metropolitan area—Dulles International Airport and Baltimore- Washington International Thurgood Marshall Airport (BWI). Dulles  opened on November 19, 1962. The federal government built Dulles,  located approximately 30 miles west of Washington, D.C., in part to  provide a facility for nonstop and connecting and international air carrier  traffic into the Washington, D.C. area. In 2005, Dulles handled 27 million  passengers. BWI, built by the city of Baltimore and originally named  Friendship International Airport, was opened on June 24, 1950. BWI,  which is owned and operated by the state of Maryland, is located 10 miles  southwest of Baltimore and approximately 30 miles northeast of  Washington, D.C. In 2005, BWI handled 19.7 million passengers.
section_title: FAA Indicates Some Additional Capacity Could Be Added, but Airports Authority Cites Airport Infrastructure Constraints as an Obstacle
paragraphs: According to FAA officials, whose estimate is based on airside capacity  (principally runways) and not landside infrastructure (such as terminals  and parking facilities), Reagan National can presently accommodate four  additional slots per hour. Airport officials disagree on the basis for FAA’s  estimate and cite the unknown future course of general aviation at the  airport and the limited capacity of airport infrastructure (such as gates,  baggage handling areas, and parking) to handle more commercial flights.  Airport officials were unsure of how many additional flights, if any, the  airport could accommodate. Even without increasing the number of slots,  there are opportunities to accommodate more flights and passengers.  Some current slots remain unused during early morning or late evening  hours, and some slots designated for air carriers are being used for smaller  commuter aircraft.
subsections: section_title: FAA Estimates Airport Can Accommodate Additional Slots
paragraphs: According to FAA, Reagan National’s overall runway capacity can  presently accommodate about four additional hourly slots above the  current slot allocation under the high-density rule. FAA continues to rely  on the DOT’s study of the high-density rule that it conducted in 1995. The  study estimated that the airport’s balanced capacity is 67 flights per hour,  or 4 more than what is currently in place, resulting in an additional 60  flights per day based on an 15-hour operating period. The study predated  the exclusion of general aviation after September 11. The study concluded  that FAA’s traffic programs and procedures could safely accommodate the  increase, but it also said the increase was likely to result in more delays. In  2004, the most current year for which this data are available, Reagan  National experienced an average delay time of 5 minutes, one of the  lowest in the nation for large hub commercial airports.
section_title: Airports Authority Questions Reagan National’s Capacity to Accommodate Additional Slots
paragraphs: Airport officials disagree with FAA’s estimate because it assumes balanced  capacity, whereas the airport prefers to measure capacity differently.  Airport officials stated any measurement of capacity should be based on  poor weather conditions and Instrument Flight Rules (IFR). FAA and  GAO believe balanced capacity is a more appropriate method for  determining an airport’s capacity than the method suggested by the  airports authority. The 1995 DOT study points out that estimating capacity  under IFR conditions, when the airfield is at the lowest level of available  capacity does not ensure steady airfield availability. In practice, this  approach would leave large amounts of airfield capacity unused because a  significantly higher capacity could be achieved during the better weather  conditions under which Visual Flight Rules (VFR) apply. According to  data from DOT, less than 1 percent of air traffic operations at Reagan  National from November 2005 to November 2006 were delayed because of  weather conditions.
Assuming capacity under IFR conditions, airport officials raised two issues  that would limit growth at the airport. The first issue is the potential return  of general aviation flights. Airport official said the absence of general  aviation flights helped the airport to absorb the additional slots that were  authorized under AIR-21 and Vision 100. After September 2001, DHS  banned general aviation flights around the national capital region. Prior  to the September 11 terrorist attacks, the airport handled 40,000 to 50,000  unscheduled aircraft flights including general aviation, annually.
Since October 2005, general aviation flights have been allowed to return,  but only under very restrictive conditions, resulting in very little activity at  Reagan National. According to airport officials, between October 2005  and August 2006, for example, the airport had fewer than 200 general  aviation flights. Figure 3 shows the level of flights of all types of aircraft  since January 2001. As the figure shows, traffic for all types dropped after  September 11, 2001, but commercial traffic (commuter and air carrier) has  basically returned to pre-September 11 levels. By contrast, general aviation  has not done so.
According to airport officials, as a result of the significantly diminished  presence of general aviation, some airside capacity remains, but  commercial aviation might not be able to use it all. A key reason is that  commercial aircraft require the longer main runway for takeoff and  landings, while many general aviation aircraft can use the shorter runways  for takeoff and landing.
The second issue airport officials raised as limiting capacity is  infrastructure limitations. These limitations involve several aspects of the  airport’s infrastructure.
Passenger Loading Gates. According to airport officials, the number of  gates affects the ability to add more slots. Every gate at the airport is  currently leased to airlines with flights at the airport, known as tenant  airlines. Airlines wishing to begin flights at the airport, known as new  entrants, can make arrangements with tenant airlines to share a gate, but a  tenant airline is not required to share its gate if its schedule does not allow  it. A recent analysis by the airport shows that some gates are available  during certain parts of the day. For example, during October 2006, some  gates were unused during both peak and nonpeak times, primarily those in  the older and less desirable terminal A. During the 18-hour operating  period, gates in terminal A were unused 46 percent of the time, while gates  in terminal B/C were unused 22 percent of the time. Most of the available  time periods are during nonpeak hours.
Terminal Facilities. Officials said Reagan National has limited capacity to  expand terminal facilities such as ticket counters and baggage handling  areas due to the lack of space on the airport property. If additional slots  are permitted, existing tenant airlines might be able to use their existing  facilities more fully, but new entrant airlines may have difficulty obtaining  the necessary terminal facilities, especially at peak periods during the day.  For the recent slots awarded under AIR-21 and Vision 100, the airports  authority has been able to accommodate new entrants with gates and  other facilities. However, airport officials said that such accommodation  has become increasingly difficult. Officials from Alaska Airlines, one of the  newer airlines at Reagan National, told us that its experience in getting the  needed facilities has been positive.
Parking Facilities. According to airport officials, limited parking at the  airport could make it difficult to accommodate additional passengers,  resulting from increased slots. Passengers have a variety of ways to access  the airport terminal, including rail transit, taxis, shuttle services, and  private car. For those who drive their own cars, the airport provides over  7,900 parking spaces. According to airport officials, the parking facility is  running at or near capacity with the existing flight schedule. For example,  over a 12-month period from November 2005 to October 2006, two of the  four parking garages reached capacity 100 days or more. In order to help  mitigate some of this pressure, the airport plans to add an additional deck  to the current parking structure. This additional parking deck would  provide 850 more spaces and is slated for completion in 2010.
section_title: Opportunities Exist to Expand Current Capacity at Reagan National
paragraphs: In two ways, Reagan National’s current capacity under the existing slot  limits could be expanded. First, the airport has available slots during  certain parts of the day, though they are for less desirable times. Of the  total 912 daily slots available for airlines, 834 are currently allocated and  approximately 78 slots are unused. Each of these unused slots falls either  in the early morning (between 6:00 and 7:00) or in the late evening  (between 9:00 and midnight), which suggests that no existing airlines and  most likely no new entrants wish to initiate new service with a schedule  limited to these hours. According to airport officials, these slots remain  unallocated because there is less demand for passenger service during  these hours and because noise restrictions after 10 p.m. require quieter  aircraft.
The second way in which current capacity could be expanded is to reduce  the number of smaller commuter planes using slots that are allocated for  larger jet planes that carry more passengers. For example, FAA data show  that in August 2006, commuter flights used nearly double the slots that  were designated for commuter flights (see table 2). For example, on one  route, between Raleigh-Durham and Reagan National, DOT data show that  in November 2006, two carriers operated an average of 26 daily flights  using commuter jets, which have a maximum capacity of 76 seats,  although larger jets were designated for the slots used for the commuter  flights. FAA and airport officials acknowledged that commuter aircraft  often use air carrier slots, but noted that this practice is permissible under  federal regulation.
section_title: Airlines with Nonstop Service between Beyond-Perimeter Airports and Reagan National Gained Significant Market Share of Traffic in Those Markets, While the Effect on Flights to Other Area Airports Is Not Evident
paragraphs: Airlines awarded slots for nonstop service between Reagan National and  airports beyond the 1,250 mile perimeter have been able to gain a  significant market share of traffic for routes. The price they charge for this  direct service is generally higher than the price for flights requiring a  connection. We did not find evidence that Dulles or BWI traffic or fares  were affected by the beyond perimeter flights to Reagan National.
For each of the six beyond-perimeter airports, the airlines awarded slots  for nonstop service between Reagan National and those airports gained  significant market share of passenger traffic over a short period of time.  For example, in the Denver market, Frontier Airlines, had no nonstop  passenger traffic between Denver and Reagan National before it was  awarded two slots (one daily roundtrip) in August 2000 and four additional  slots (two more daily roundtrips) in 2004, and it now has garnered nearly  60 percent of the passenger traffic to Reagan National from Denver (see  table 3). United Airlines, which was awarded two slots (one daily  roundtrip) in the same market in 2004, now has 15 percent of the market.  Between Frontier and United Airlines, the two carriers’ nonstop routes  have nearly three-fourths of the Denver-Reagan National traffic.
Airlines with beyond-perimeter slots generally charge higher fares than are  charged for connecting flights to and from Reagan National (see table 4).  In half of the cases the nonstop fare was on average $25 to $50 higher than  the connecting flight fares to and from Reagan National. Los Angeles is the  only market in which the average direct fare is less than the average fare  for flights with connections.
subsections: section_title: The Effect of Beyond- Perimeter Slots on Area Airports Is Not Evident
paragraphs: We did not find evidence that beyond-perimeter flights to and from Reagan  National affected flights from the same airports to or from Dulles or BWI.  We analyzed fare and passenger data for flights between Dulles and BWI  and those airports and for all traffic serving Dulles and BWI. In doing so,  we observed that the data did not produce any distinguishable trends or  patterns that would indicate that beyond-perimeter slots at Reagan had  any effect on fares or passenger levels at either Dulles or BWI.
Overall, Dulles has experienced growth in traffic and a decline in fares,  while BWI has experienced little overall change in traffic or fares from  1999 to 2005. To assess whether the introduction of new nonstop beyond- perimeter routes into Reagan National affected service between the same  six airports and Dulles or BWI, we compared the percentage change in  average fares and total passengers, from 1999 through 2005 for travel  between each of the six beyond-perimeter airports and Dulles and BWI  against the overall percentage change in annual average fares and  passengers for all traffic serving Dulles and BWI. As the figures below  illustrate, some routes experienced greater or lesser changes relative to  overall changes at the airport, but no consistent trends were apparent.
Dulles annual airport passenger traffic grew from 1999 to 2005, from 19.7  million to 27 million, a 37 percent increase. We did not find any patterns or  trends that would suggest that the changes to the perimeter rule at Reagan  National had affected fares or service between Dulles and these six  airports. (See figs. 4 and 5). Airports authority officials stated they had no  reason to believe that these limited beyond-perimeter awards affected  Dulles. Rather, the officials noted, the airport’s fares and passenger traffic  were significantly affected by its experience with low-fare carrier,  Independence Air, which had a large growth of flights at Dulles but has  now gone out of business.
For overall passenger traffic between Dulles and the six airports, as figure  4 shows, we did not find evidence that the beyond-perimeter slots at  Reagan National affected passenger levels. For example, passenger traffic  between Dulles and some airports grew faster than overall airport traffic  despite the introduction of nonstop flights to Reagan National.
BWI airport passenger traffic grew from 17.4 million in 1999 to 19.7 million  in 2005. But, similar to Dulles, we found no patterns or trends in  passengers or fares between BWI and the six airports that would suggest  that changes to the beyond-perimeter rule at Reagan National had an  impact on flights at BWI. (See figs. 6 and 7). Officials from BWI stated that  changes to the slot and perimeter rule did not adversely affect BWI and  noted other factors, notably US Airways reduction of its commuter service  at BWI.
section_title: Agency Comments
paragraphs: We provided copies of this report to DOT and the airports authority. We  received comments from the Office of the Deputy Assistant Secretary for  Aviation and International Affairs, Department of Transportation. DOT  acknowledges that all available slots at Reagan National Airport are not  used to maximum effect and agreed that there are a number of reasons for  this, including curfew restrictions, the commercial viability of slots in the  early morning or late evening under current regulations, and the  concentration of the majority of slot holdings among a relatively small  number of carriers. DOT also recognizes that the underutilization of slots  is exacerbated by the fact that carriers can use commuter aircraft in slots  designated for large aircraft but are legally prohibited from using large  aircraft in slots designated for commuter aircraft. In addition, other  statutory restrictions, such as the perimeter rule, contribute to the  underutilization of slots and prevent market forces from producing the  maximum public benefit from these scarce assets. For example, the early  departure and late arrival times at other airports are often used by airlines  to operate overnight “red eye” or other long-haul flights. Regulations  governing operations at Reagan National, such as the perimeter rule,  prevent carriers from using such scheduling and fleet assignment  techniques to maximize the value of slots and facilities at that airport.  While we do not disagree with DOT’s observations, we also recognize that  any changes in the commuter slot or perimeter rules at Reagan National  would have competitive implications for airlines and the communities they  serve. Assessing these effects was beyond the scope of our study. Finally,  DOT offered technical comments, which we have incorporated as  appropriate.
The airports authority commented that with one exception the report  accurately reflects the situation at Reagan National. While the airports  authority believes that the airport can accommodate some additional  capacity, it is something less than the 4 slots per hour as suggested by  DOT. The airports authority still disagrees with the basis for DOT’s 1995  estimate of 67 slots per hour under the High-Density Rule, just as it did in  response to our 1999 report on this matter. The airports authority believes  that maximum capacity should be based on IFR conditions, that is,  capacity under adverse weather conditions. Instead, DOT bases its  estimate of maximum capacity on a mix of IFR and VFR traffic, a  methodology that we endorsed in 1999 and still do today. We believe, as  does DOT, that balanced capacity is a superior method for determining the  airport’s capacity because it accounts for the operation of aircraft during  all weather conditions. The airports authority offered technical comments,  which we have incorporated as appropriate. The airports authority’s  comments, along with our responses to them appear in appendix II.
As agreed with your office, unless you publicly announce the contents of  this report earlier, we plan on no further distribution until 3 days from the  date of this letter. At that time, we will send copies of this report to the  Secretary of Transportation and the Administrator of the FAA. We will  also make copies available to others upon request. In addition, the report  will be available at no charge on the GAO Web site at http://www.gao.gov.
If you or your staff have any questions about this report, please contact me  at (202) 512-4803 or dillinghamg@gao.gov. Contact points for our Offices  of Congressional Relations and Public Affairs may be found on the last  page of this report. Staff who make key contributions to this report are  listed in appendix II.
section_title: Appendix I: Scope and Methodology
paragraphs: To determine how many additional slots Reagan National Airport can  accommodate, we analyzed Federal Aviation Administration (FAA) and  Metropolitan Washington Airports Authority (airports authority)  operational data, reviewed prior capacity studies, and interviewed airports  authority, FAA, and Department of Transportation (DOT) officials. This  analysis included reviewing data on the number and type of aircraft using  the slots and how this usage was dispersed during the day and by which  runway. We also reviewed the data contained in the 1995 study done by  the DOT on the high-density rule and reviewed the basis for DOT’s  capacity estimates. In addition, we analyzed airports authority gate  utilization data and airline leases to determine the extent to which gate  space at the airport is unused. Finally, we interviewed officials from the  DOT, FAA, airports authority and other stakeholders about Reagan  National’s current and future capacity.
To assess traffic between Washington, D.C., area airports and the six  beyond-perimeter airports for which nonstop service to Reagan National  was awarded since 1999, we analyzed DOT’s Origin and Destination ticket  data; we used these data to examine changes in fares and passenger levels  between Reagan National, Dulles International (Dulles) and Baltimore- Washington Thurgood Marshall International Airport (BWI), and these  airports. We also interviewed airports authority and BWI officials. For this  analysis, we conducted a historical look at traffic between the six airports  and the three Washington-Baltimore area airports. We obtained the ticket  data from BACK Aviation Solutions, a private contractor that provides  these data to interested parties. We used these data to examine trends in  passenger and fares to identify any changes in traffic and fares between  the six beyond-perimeter airports and Reagan National, Dulles and BWI  airports. To assess the reliability of these data, we reviewed the quality  control procedures applied to these data, and subsequently determined  that the data were sufficiently reliable for our purposes. We conducted our  review from July 2006 through February 2007 in accordance with generally  accepted government auditing standards.
section_title: Appendix II: Comments from the Metropolitan Washington Airports Authority
paragraphs: The following is GAO’s comment on the Metropolitan Washington Airports  Authority’s (airports authority) February 1, 2007, letter.
subsections: section_title: GAO Comment
paragraphs: We believe, as does DOT, that “balanced capacity” is a more appropriate  method for determining an airport’s capacity than the method suggested  by the airports authority. While the airports authority contends that  Instrument Flight Rules (IFR) should be used to measure capacity, DOT’s  Technical Supplement No. 3 to its 1995 report points out that IFR airfield  capacity is indicative of the lowest level of available capacity, and thus  virtually ensures constant availability of an airfield. In practice, this  approach would leave large amounts of airfield capacity unused because a  significantly higher capacity could be achieved during the better weather  conditions under which Visual Flight Rules apply. According to data from  FAA, less than 1 percent of all air traffic operations at Reagan National  from November 2005 to November 2006 were delayed because of weather  conditions. Because setting the number of slots on the basis of balanced  capacity reflects both bad and good weather conditions, we did not revise  our report.
section_title: Appendix III: GAO Contact and Staff Acknowledgments
subsections: section_title: GAO Contact
section_title: Staff Acknowledgments
paragraphs: In addition to the individual named above, Ed Laughlin, Assistant Director;  Paul Aussendorf; Jay Cherlow; Dave Hooper; Nick Nadarski; Josh  Ormond; and Stan Stenersen made key contributions to this report.