USE OF THE 

NATIONAL AIRSPACE SYSTEM 

Federal Aviation Administration 

Report Number: CR-2008-028 

Date Issued: March 3, 2008 
U.S. Department of 

Memorandum

Transportation 

Office of the Secretary 

of Transportation 

Office of Inspector General 

Subject: INFORMATION: Use of the National 

Airspace System 

Federal Aviation Administration 

Report Number CR-2008-028 

Date: March 3, 2008 

From: David Tornquist 

Assistant Inspector General 

 for Rail and Maritime Program Audits and 

 Economic Analysis 

Reply to 

Attn. of: JA-50 

To: Acting Federal Aviation Administrator 

This report presents the results of our audit of the use of the National Airspace 

System (NAS). The House Committee on Transportation and Infrastructure 

requested this audit to provide policymakers with a common understanding of who 

uses the NAS as they consider how to finance the aviation system into the future. 

Disagreement among stakeholders regarding their use of the NAS makes it 

difficult to evaluate Federal Aviation Administration (FAA) financing alternatives. 

Our specific objectives were to determine: (1) how different groups use NAS 

elements, (2) how that usage contributes to aviation congestion, (3) whether NAS 

users can be grouped in a meaningful manner based on their usage of the system, 

and (4) how good a proxy is jet fuel for use of FAA air traffic services. 

We examined FAA fiscal year (FY) 2005 flight activity data1

 and other data 

regarding the use of FAA tower, terminal, and en route services by different 

aircraft types and user groups. We also assessed the relationship between jet fuel 

consumption and use of FAA’s air traffic control services in several representative 

markets. A detailed discussion of our scope and methodology is included in 

Exhibit A. We conducted this audit in accordance with generally accepted 

Government Auditing Standards prescribed by the Comptroller General of the 

United States. We did not systematically audit or validate the data in any of the 

 

1

 FY 2005 is the latest flight activity data available from FAA that contains the corrected identification of aircraft 

engine type and operator classification necessary to undertake this analysis. 
2

databases. However, we conducted trend analyses and checks of the data to assess 

reasonableness and comprehensiveness. We also spoke with managers responsible 

for maintaining the databases to understand any noted inconsistencies and attempt 

to resolve them. Based on our understanding of the data through discussions with 

knowledgeable agency officials, as well as checks for obvious errors in accuracy 

and completeness, we determined that the data was sufficiently reliable for our 

purposes. 

BACKGROUND 

Currently, NAS users pay the vast majority of FAA’s costs through ten aviationrelated excise taxes, including taxes on airfares, fuel and cargo. Almost 68 percent 

of the revenue from these taxes in FY 2006 derived from the 7.5 percent ticket tax 

and the then $3.30 segment tax in calendar year (CY) 2006.2

 All of the aviation 

excise taxes supporting FAA’s programs will expire on June 30, 2008.3

 Congress 

is currently deliberating on whether to continue, replace, or modify these excise 

taxes as part of its ongoing effort to reauthorize the FAA. 

Aviation stakeholder groups strongly disagree on their relative use of the aviation 

system and contribution to aviation congestion. Air carrier representatives argue 

that non-air carriers are significant NAS users and as such contribute to aviation 

congestion and the resultant system delays. Non-air carrier representatives, 

particularly general aviation and “business jet” groups, claim that they do not 

make significant use of the NAS, are marginal users to the system, and do not 

contribute to aviation congestion because they avoid congested airports and 

airspace. 

This disagreement on NAS usage leads to similar disagreements as to the relative 

share of FAA’s costs that each stakeholder group should pay.4

 Air carriers claim 

that they are being unfairly required to pay 

more than their use of the NAS and FAA 

services would justify. As a result, they 

claim that they are subsidizing non-air 

carriers’, in particular business jet 

operators’, NAS usage. Conversely, 

general aviation and business jet operators 

contend they are paying their fair share for 

their relative use of the system. 

Air Carriers are scheduled and charter 

airlines, usually operating jet or 

turboprop aircraft with more than 30 

seats. 

Non-Air Carriers are general aviation, 

fractional (shared) ownership, and ondemand air-taxi operators using aircraft 

with less than 30 seats. 

 

2

 The segment tax rose to $3.40 in calendar year 2007. 

3

 These taxes were scheduled to expire on September 30, 2007. Congress extended them through a series of 

Continuing Resolutions, the most recent of which expires on June 30, 2008. 4

 Another factor relevant to the policy decision on the amounts that user groups should pay for FAA services is the 

cost of providing individual FAA services at different locations using different staff and equipment. This report does 

not address the cost of providing individual services. 
3

On March 21, 2007, we testified5

 on the use of the NAS before the House 

Transportation and Infrastructure Committee’s Aviation Subcommittee; our 

testimony also included our observations on the Administration’s FAA financing 

proposal.6

 In lieu of the Administration’s FAA financing proposal, the Senate 

Commerce Committee passed the Aviation Investment and Modernization Act of 

2007 (S. 1300). In addition, the Senate Finance Committee, which has jurisdiction 

over the aviation excise taxes, passed its title of the FAA financing legislation. 

However, the Senate as a whole has not passed a long-term FAA program 

reauthorization and financing bill at this time. The House passed the FAA 

Reauthorization Act of 2007 (H.R. 2881), which incorporates both program 

authorization and tax provisions. 

The Administration’s proposal would alter the structure of fees and taxes paid by 

air carriers and non-air carriers, reflecting FAA’s conclusion that the revenues 

recovered from users should be more closely linked with the cost of providing air 

traffic services. The Senate Commerce and Finance Committee proposals would 

change the structure of fees and taxes of non-air carriers to a lesser degree. The 

House proposal fundamentally maintains the current structure of taxes among the 

user groups. 

RESULTS IN BRIEF 

We found that air carriers and non-air carriers, including general aviation and 

business jet operators, all make sufficient use of the NAS so as to materially 

contribute to FAA’s costs and congestion in general. We also found alternative 

NAS user groupings that are more homogeneous in terms of their use of FAA 

services than the groupings reflected in the current aviation excise tax structure. 

Finally, we found that jet fuel consumption is a better proxy for the use of the 

NAS than the current aviation excise taxes, but it does not measure whether air 

traffic control services are used, nor does it distinguish between the types and 

complexities of services used. 

All Aircraft Groupings by Engine or Operator Type Make Significant 

Use of the NAS 

We examined use of the NAS in two ways: by aircraft powered by different 

engine type and by aircraft flown by different operator types. We found that all of 

the groups examined made significant use of FAA air traffic control services. 

 

5

 OIG Testimony Number CC-2007-034, “FAA’s Financing Proposal,” March 21, 2007. OIG reports and testimonies 

are available on our website: www.oig.dot.gov. 6

 The Next Generation Air Transportation Financing Reform Act of 2007 (S. 1076). 
4

Piston Engine Airplanes and Rotorcraft Make Significant Use of the NAS. 

While jets and turboprops were the major users of the NAS, piston engine 

airplanes and rotorcraft accounted for 41 percent of FAA tower services7

 and 

31 percent of FAA terminal area control services in FY 2005 (see figure 1). 

However, since piston engine airplanes and rotorcraft typically operate at lower 

altitudes, they only utilized 4 percent of en route services. 

Figure 1. Use of Air Traffic Control Services 

by Aircraft Type - FY 2005 

46%

55%

89%

13% 14%

7%

41%

31%

4%

0%

20%

40%

60%

80%

100%

Percent of Operations

Tower Terminal En Route

 Jet Turboprop Piston/Rotor Jet Turboprop Piston/Rotor Jet Turboprop Piston/Rotor 

Source: OIG Analysis of FAA Stakeholder Data Package 

Non-Air Carriers Make Significant Use of the NAS. Non-air carriers were the 

major users of FAA tower and terminal area control services in FY 2005, 

accounting for 59 percent and 49 percent respectively of these services. However, 

air carriers were the major users of FAA en route services, accounting for 

79 percent of the total (see figure 2 on the following page). 

 

7

 FAA services were measured in terms of operations, i.e., an aircraft handled by an air traffic control facility. For a 

tower, this was a landing or take-off. For terminal area radar, this was an instrument approach, departure or other 

control within the terminal airspace. For en route, this was a mile flown under positive en route control. 
5

Figure 2. Use of Air Traffic Control Services 

by Operator Group - FY 2005 

35%

44%

79%

59%

49%

17%

6% 7% 4%

0%

20%

40%

60%

80%

100%

Percent of Operations

Tower Terminal En Route 

 Carrier Non-air Public 

 carrier 

 Carrier Non-air Public 

 carrier 

 Carrier Non-air Public 

 carrier 

Source: OIG Analysis of FAA Stakeholder Data Package 

We found that non-air carriers tend to avoid large primary metropolitan airports. 

Overall, at the 268

 large primary airports we examined, air carriers accounted for 

93 percent of all operations. Operations by non-air carriers at these airports 

ranged from as little as 1 percent to as high as 20 percent. However, we also 

found that non-air carriers have significant operations at the most active towers in 

the country (as determined by number of operations). More than half (53 percent) 

of non-air carrier operations occurred at the top third (162) most active towered 

airports (see table 4 on page 10). Finally, 77 percent of all operations at the twothirds of towers with the lowest activity were attributable to non-air carriers. 

Business Jets’ NAS Usage Is Considerable. FAA does not track business jets as 

a separate NAS user group. However, we disaggregated FAA’s data in two 

different ways that shed light on the current debate among stakeholder groups 

representing air carriers and business jet operators about business jets’ NAS usage. 

A broader categorization that approximates business jets is non-air carrier jets (jets 

operated by corporations, individuals, and air taxis and under fractional or shared 

ownership arrangements). These jets accounted for 12 percent of tower and 

13 percent of terminal area control services in 2005. In comparative terms, nonair carrier jets use of tower and terminal area control services is about one-third of 

air carrier jets and turboprops. A narrower categorization of business jets is 

general aviation jets, which excludes air taxis and fractionals. These accounted for 

 

8

 Four of the 30 large primary airports were not included in this analysis. Washington Reagan is general aviation 

restricted. The data for Minneapolis-St. Paul was incomplete. The data for San Diego was not provided, and 

Honolulu is geographically unique. 
6

9 percent of tower and 7 percent of terminal area control services in 2005 (see 

tables 1 and 2 on pages 8 and 9). 

Both Air Carriers and Non-Air Carriers Contribute to Aviation 

Congestion

We examined congestion9

 at several of the most active towers, terminal radar 

approach control (TRACON) facilities, and en route centers. We found that air 

carriers accounted for the majority of activity and congestion at the 26 large 

primary metropolitan airports, with non-air carriers contributing, but to a far lesser 

degree. Air carriers and non-air carriers contributed to congestion at the terminal 

control areas we examined. For example, non-air carriers accounted for 20 to 

30 percent of the peak level of instrument approach operations at the New York 

TRACON (see figure 5 on page 14). Both commercial and general aviation 

operators contributed to congestion at the heavily used en route centers we 

examined. For example, general aviation operations accounted for 18 percent to 

23 percent of operations at the Cleveland en route center during peak times of the 

day (see figure 6 on page 15).

NAS Users Can Be Grouped More Homogeneously Than Reflected in 

the Current Aviation Excise Tax Structure 

The current aviation excise taxes do not group NAS users homogeneously in terms 

of their use of the NAS. For example, the current tax structure groups jets used for 

non-commercial purposes with general aviation piston engine airplanes, although 

they are taxed at different rates. However, those jets are likely to have more in 

common (in terms of NAS usage) with commercial jets, which are taxed 

differently. Certain aircraft and operator types have distinct operating 

characteristics that could form the basis of more homogeneous groupings. Jet and 

turboprop aircraft have different operating characteristics than piston engine 

airplanes and rotorcraft. Similarly, air carrier operators have different operating 

characteristics than non-air carriers. Grouping users by aircraft or operator type 

would be more indicative of NAS usage than the distinctions inherent in the 

current excise tax structure. 

A Tax Based on Fuel Consumption Would Approximate NAS Usage, 

but it Does Not Measure Use of Air Traffic Control Services 

We found that a tax based on fuel consumption is a better barometer of NAS 

activity than the current excise taxes because it would recover costs from users 

 

9

 We measured congestion by examining the demand for specific air traffic services at the busiest times of day. For 

towers, we examined arriving flight operations. For TRACONs, we examined instrument approach operations. For 

en route centers, we examined operations. 
7

more in proportion to their system activity than excise taxes. For example, our 

examination of the Las Vegas to Los Angeles flight market found that commercial 

aircraft accounted for 90 percent of all aircraft activity. However, commercial 

aircraft paid 99 percent of the excise taxes currently collected. This share would 

decline to 94 percent under a fuel-only tax. However, a fuel tax is not a perfect 

proxy for NAS activity since fuel consumption can vary in proportion to factors 

unrelated to that activity, such as aircraft weight. In addition, a tax based on fuel 

consumption neither measures whether ATC services are used nor distinguishes 

among the types and complexities of the services used. Similarly, the current 

ticket, segment, and freight waybill taxes do not vary according to the complexity 

or amount of ATC services consumed. 

FINDINGS 

All Aircraft Groupings By Engine or Operator Type Significantly Use 

the NAS. 

We examined use of the NAS in two ways: by aircraft powered by different engine 

types (jet, turboprop, and piston/rotor) and by aircraft flown by different operator 

types (air carrier, non-air carrier, and public use). We found that none of the 

groups examined were marginal users of FAA air traffic control services. 

Piston Engine Airplanes and Rotorcraft Significantly Use the NAS 

We examined NAS usage by 

aircraft type and found that 

piston engine airplanes and 

rotorcraft were significant NAS 

users, accounting for 41 percent 

of tower, 31 percent of terminal, 

and 4 percent of en route 

services in FY 2005. Turboprop 

aircraft accounted for 13 percent 

of tower, 14 percent of terminal, 

and 7 percent of en route 

services. Jet aircraft were the 

largest users of FAA services, 

accounting for 46 percent of 

tower, 55 percent of terminal, 

and 89 percent of en route 

services (see figure 1 on 

page 4). 

Tower services manage ground operations on airport 

taxiways and runways as well as departure and 

landing activity in airspace within about 5 miles of the 

airport. The sophistication of services ranges from 

visual-only control, at the majority of airports, to 

radar and instrument landing aids at the larger air 

carrier airports. 

Terminal Area Control services are provided to 

aircraft in an area that rises up to 10,000 feet and 

expands to a 30 to 50 mile radius of major airports. 

Aircraft are provided instrument approaches to and 

departures from the primary and secondary airports 

within the terminal control area or managed while 

transiting the terminal area airspace. 

En Route Control services provide positive control 

for all aircraft flying above 18,000 feet and those 

flying below that level, but operating under Instrument 

Flight Rules (IFR) conditions and oceanic air traffic 

control for the 80 percent of controlled international 

airspace under FAA management. 
8

Non-Air Carriers Significantly Use the NAS 

We also examined NAS usage by operator type and found that in FY 2005 non-air 

carriers exceeded air carriers in their use of FAA tower and terminal area control 

services, but not en route services. Non-air carriers accounted for 59 percent of 

tower, 49 percent of terminal, and 17 percent of en route services. Air carriers 

accounted for 35 percent of tower services, 44 percent of terminal, and 79 percent 

of en route services. Public users10 accounted for 6 percent of tower services, 7 

percent of terminal area control services, and 4 percent of en route services. 

We also found that non-air carriers accounted for 93 percent of the aircraft 

contacts made by flight service stations in FY 2005. While general aviation 

operators accounted for 75 percent of the total contacts, fractionals and air taxis 

accounted for 18 percent of the total contacts.11 Users of these services are mostly 

light aircraft operators, not airlines or corporate aircraft operators that contract for 

weather and flight dispatch services or employ their own staff to handle these 

functions. 

Non-air carrier piston engine airplanes and rotorcraft were the largest users of 

FAA tower services in FY 2005, accounting for 40 percent of all services. Their 

usage of tower services was 33 percent higher than the next highest user group, air 

carrier jets, which accounted for 30 percent of tower service usage. Non-air 

carrier jets also accounted for considerable tower service usage at 12 percent (see 

table 1). 

Table 1. Tower Services Usage – FY 2005 

Percent of Tower Operations by User Category and Aircraft Type

User Jet Turboprop Piston/Rotor User Total 

Air Carrier 30% 4% 1% 35% 

Non-Air Carrier 

(General Aviation) 

12% 

(9%) 

7% 

(5%) 

40% 

(38%) 

59% 

(51%) 

Public Use 4% 1% 1% 6% 

Aircraft Total 46% 13% 41% 100% 

Source: OIG Analysis of FAA Stakeholder Data Package 

Percentages may not add due to rounding. 

 

10 Public users are military, governmental, and medical flight operators. 

11 Fractional operators are shared ownership arrangements, and air taxis are on-demand charter operators. 
9

Air carrier jets were the largest users of terminal area control services in FY 2005, 

accounting for 38 percent of those services. Their usage was 31 percent greater 

than the next highest user, non-air carrier piston engine airplanes and rotorcraft, at 

29 percent (see table 2). Non-air carrier jet usage of terminal area control services 

was 13 percent. 

Table 2. Terminal Area Control Services Usage – FY 2005 

Percent of Approach Control Operations by User Category and Aircraft Type

User Jet Turboprop Piston/Rotor User Total 

Air Carrier 38% 5% 1% 44% 

Non-Air Carrier 

(General Aviation) 

13% 

(7%) 

7% 

(3%) 

29% 

(22%) 

49% 

(33%) 

Public Use 4% 2% 1% 7% 

Aircraft Total 55% 14% 31% 100% 

Source: OIG Analysis of FAA Stakeholder Data Package 

Percentages may not add due to rounding. 

Air carrier jets dominated the use of en route services in FY 2005, accounting for 

75 percent of those services. Their usage was almost seven times that of the next 

largest user, non-air carrier jets, at 11 percent (see table 3). 

Table 3. En Route Control Services Usage – FY 2005 

Percent of Aircraft Miles Controlled by User Category and Aircraft Type

User Jet Turboprop Piston/Rotor User Total 

Air Carrier 75% 3% 0% 79% 

Non-Air Carrier 

(General Aviation) 

11% 

(5%) 

3% 

(2%) 

4% 

(3%) 

17% 

(10%) 

Public Use 3% 1% 0% 4% 

Aircraft Total 89% 7% 4% 

Source: OIG Analysis of FAA Stakeholder Data Package 

100% 

Percentages may not add due to rounding. 

We found that non-air carriers tend to avoid certain large primary metropolitan 

airports. Overall, at the 26 large primary airports we examined, air carriers 

accounted for 93 percent of all operations. Operations by non-air carriers at these 

airports ranged from as little as 1 percent to as high as 20 percent. However, we 

also found that non-air carriers have significant operations at the most active 
10

towers in the country (as determined by number of operations), many of which 

surround large primary airports. 

While 87 percent of air carrier operations were at the top third most active towers 

(162 airports), more than half (53 percent) of non-air carrier operations also 

occurred at these airports. Total activity at the top third most active towers was 

split almost evenly between air carrier and non-air carrier operations. Finally, 

77 percent of all operations at the two-thirds of airports with the lowest activity 

were attributable to non-air carriers (see table 4). 

Some towered airports exclusively used by non-air carrier operators are among the 

busiest towers in the country in terms of flight operations. Of the 40 most active 

towers in the country, nine are nearly exclusive non-air carrier facilities. For 

example, in FY 2005, Denver Centennial Airport, a reliever to Denver 

International Airport, had more operations than New York John F. Kennedy 

Airport, and Deer Valley Airport, in Phoenix, had more tower operations than 

either Orlando International or San Francisco International Airports. 

Table 4. Operations at Towered Airports - FY 2005 

% of Tower 

Operations 

% of Carrier 

Operations 

Air Carrier Non-Carrier Public 

1/3 Most Active 

Towers 

48% 

87% 

50% 

53% 

3% 

33% 

2/3 Least Active 

Towers 

13% 

13% 

77% 

47% 

10% 

67% 

Source: OIG Analysis of FAA Stakeholder Data Package 

Percentages may not add due to rounding. 

Business Jets’ NAS Usage Is Considerable 

The structure of taxes on “business” or “corporate” jets has become a lightening 

rod in the debate regarding how to finance the FAA. Under the current system of 

aviation excise taxes, the same flight can be charged a significantly different 

amount depending upon the purpose for which the flight is made. An aircraft 

flown by a scheduled air carrier will be charged the 7.5 percent ticket tax and the 

$3.30 (CY 2006) per passenger flight segment fee. The same aircraft, privately 

owned, would likely impose similar costs on FAA, but would pay less than the 

scheduled airlines for those same services through the general aviation fuel tax. 
11

Air carrier representatives argue that it is unfair for their passengers and 

themselves to subsidize these business jets. However, the National Business 

Aviation Association contends that only 3 percent of general aviation aircraft that 

are used for business purposes actually belong to Fortune 500 companies (i.e. are 

“corporate jets”) and business aircraft tend to avoid congested primary airports in 

favor of reliever or business airports. As a result, these stakeholders contend that 

the current scheme by which business aircraft are charged for air traffic services is 

both fair and appropriate. 

FAA does not track business jets as a separate NAS user group. This would be 

difficult as it requires determining whether or not a particular flight was taken for 

business purposes. However, we disaggregated FAA’s data in two different ways 

that shed light on the current debate regarding business or corporate jets’ NAS 

usage. 

The first, broader categorization that approximates business jets is non-air carrier 

jets (jets operated by corporations, individuals, and air taxis and under fractional 

or shared ownership arrangements). This categorization will necessarily include a 

small number of jet aircraft that are owned by individuals or corporations, but used 

for recreational or non-business purposes. This categorization is significantly 

smaller than the category of “business aircraft” used by some stakeholder groups, 

which includes a significant number of piston engine airplane and rotorcraft 

operations. Non-air carrier jets accounted for 12 percent of tower and 13 percent 

of terminal area control services in 2005 (see figure 3). 

Figure 3. Jet Use of Air Traffic Control Services - FY 2005 

30%

38%

75%

12% 13% 11%

4% 4% 3%

0%

20%

40%

60%

80%

100%

Percent of Operations

Tower Terminal En Route

 Carrier Non-air Public 

 carrier 

 Carrier Non-air Public 

 carrier 

 Carrier Non-air Public 

 carrier 

Source: OIG Analysis of FAA Stakeholder Data Package 
12

The second, narrower categorization of business jets is general aviation jets. This 

narrower categorization more closely approximates “corporate jets” used by some 

stakeholder groups as opposed to our definition of business jets. Under this 

narrower definition, non-air carrier general aviation jets accounted for 9 percent of 

tower and 7 percent of terminal area control services in 2005. To put this in 

perspective, under both categorizations, these proxies for business jets’ tower and 

terminal area control services in FY 2005 was about one-third of air carrier jets. 

We did find support for the argument by representatives of business jet operators 

that business jets do not generally use large primary airports. As stated 

previously, the majority of tower operations at these primary airports are air 

carrier. However, business jets’ use of the NAS in total is not insignificant. As 

we stated in our March 21, 2007 testimony, based on our analysis of NAS usage, 

the use of FAA air traffic services by commercial operators, general aviation 

operators, and public users is sufficient to warrant separate cost allocation 

categories. None of these groups had activity levels low enough to support a 

conclusion that they did not materially contribute to FAA’s costs. 

Air Carriers and Non-Air Carriers Contributed to Congestion 

We measured congestion by examining the demand for specific air traffic services 

at the busiest times of day. For towers, we examined arriving flight operations. 

For TRACONs, we examined instrument approach operations. For en route 

centers, we examined operations. We found that air carriers dominate tower 

activity at most of the large primary metropolitan airports and were responsible for 

most of the congestion. Non-air carriers contributed to congestion at the busy 

terminal control and en route facilities we examined, and less significantly at large 

primary metropolitan airports. 

Demand for Tower Services at Large Airports 

Air carriers account for the majority of tower operations at the large, primary 

metropolitan airports. Non-air carrier operators tend to use other airports in the 

metropolitan area surrounding the large primary airports. At 26 large hub 

(primary) airport towers, air carriers accounted for an overall average of 

93 percent of operations, ranging from 78 percent to 99 percent. While non-air 

carriers accounted for less than 4 percent of tower operations at 11 of the 26 

airports we reviewed, at other large primary airports the percent of non-air carrier 

operations ranged from 6 percent to as high as 20 percent of operations. 

 

In terms of time of day operations, we found that at the three primary airports in 

the New York metropolitan area, hourly demand for terminal area control services 

increased, starting at 7:00 a.m., and peaked between 2:00 p.m. and 6:00 p.m. 
13

These are popular arrival times for travelers returning to New York or connecting 

to departing international flights at Kennedy. Air carriers account for the bulk of 

operations during these peak time periods, and therefore account for the majority 

of congestion. Non-air carriers account for a small amount of this activity (see 

figure 4), but do exhibit similar time of day peaking, and as such, do contribute to 

congestion. We found similar results for the other large primary airports we 

examined. 

Figure 4. New York Terminal Control Area - FY 2005 

Arriving Flight Operations by Hour of Day 

(LaGuardia, Newark, and John F. Kennedy)

0

20

40

60

80

100

120

 7AM 8AM 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM 6PM 7PM 8PM 9PM 10PM

non-air carrier air carrier

Average Hourly Arrivals

Source: OIG Analysis of FAA Data 

Demand for Terminal Area Services 

We found that both air carriers and non-air carriers contributed to congestion at 

the terminal area radar facilities we examined.12 These facilities provide terminal 

area radar services for both the primary and secondary airports within their areas 

of coverage. Therefore, even though air carriers and non-air carriers may tend to 

use different airports in a metropolitan area, they use the same TRACON facility. 

For example, the New York TRACON facility handles three large primary 

airports,13 primarily serving air carriers, and 12 outlying towered airports, 

primarily serving non-air carriers. Non-air carriers accounted for 20 percent to 

30 percent of the peak level of instrument approach operations at the New York 

TRACON. 

 

12 Terminal area radar control services are provided by terminal radar approach control (TRACON) facilities located 

within the primary airport’s control tower or in a separate facility. 13 La Guardia, Kennedy, and Newark. 
14

Air carrier and non-air carrier demand for terminal area radar services exhibited 

the same peaking during the prime travel times of the day at the metropolitan areas 

we examined. In other words, both air carriers and non-air carriers were 

competing for terminal area control services during the same busy, congested time 

periods. For example, at the New York TRACON, non-air carriers exhibited the 

same time of day peaking in demand for terminal services as did air carriers (see 

figure 5). We found the same patterns of terminal service use by non-air carriers, 

including time of day peaking, in our examination of activity at the Chicago 

TRACON. 

Figure 5. New York Terminal Control Area – FY 2005 

Instrument Approach Operations by Hour of Day 

(Includes Outlying Airports)

0

20

40

60

80

100

120

140

verage Hourly Arrivals A

7AM 8AM 9AM 10AM 11AM 12PM 1PM 2PM 3PM 4PM 5PM 6PM 7PM 8PM 9PM 10PM

non-air carrier air carrier

Source: OIG Analysis of FAA Data 

Demand for En Route Services 

We found that both commercial and general aviation operators contributed to 

congestion at the two heavily used en route centers we examined. General 

aviation operators’ use of en route services was not insignificant. Their demand 

for air traffic control services peaked during the busy periods at the en route 

centers. Due to data limitations, we included fractional and air taxi services with 

air carriers in a “commercial” category and presented general aviation separately 

in the en route time of day demand analysis. 
15

As shown in figure 6, 80 percent of operations during July 2005 at the Cleveland 

en route center were attributable to commercial operators and 17 percent of 

operations were attributable to general aviation. In addition, general aviation 

operations accounted for an even higher share of total operations, between 

18 percent and 23 percent, during the most congested times. 

Figure 6. En Route Center Operations by Hour of Day 

Cleveland Center – July 2005 

0

100

200

300

400

500

12A

General A viat ion

18 % - 2 3 %

at peak hours

Average Daily Operations

Source: OIG Analysis of FAA Data 

We found the same pattern of usage at the Atlanta en route center. 

Seventy-five percent of operations during July 2005 were attributable to 

commercial operators and 21 percent of operations were attributable to general 

aviation. As in Cleveland, the share of operations at the Atlanta en route center 

attributed to general aviation during peak periods ranged from 21 percent to 

28 percent (see figure 7 on the following page). 

M

AM

1:

2:AM

AM

3:

4:AM

5:

6:A

7:

9:

10

11

12P

1:

2:

3:

4:P

5:

6:P

7:

8:PM

9:

10P

1

A

1

M

M

AM

8:AM

AM

AM

AM

M

PM

PM

PM

M

PM

M

PM

PM

M

PM

verage Daily Operations

A

 12AM 2AM 4AM 6AM 8AM 10AM 12PM 2PM 4PM 6PM 8PM 10PM

public general aviation commercial
16

Figure 7. En Route Center Operations by Hour of Day 

Atlanta Center – July 2005 

0

100

200

300

400

500

12A

General A viat ion

2 1% - 2 8 %

at peak hours

Average Daily Operations

Source: OIG Analysis of FAA Data 

NAS Users Can Be Meaningfully Grouped Based on Their System 

Usage 

Certain aircraft and operator types have distinct operating characteristics that form 

the basis of meaningful groupings. For example, jet and turboprop aircraft share 

different operating characteristics than piston engine airplanes and rotorcraft. Jet 

and turboprop aircraft have greater altitude capacity and usually employ more 

sophisticated navigational aids that make greater use of more complex air traffic 

control services. Piston engine airplanes and rotorcraft usually fly at lower 

altitudes than jet and turbo-prop aircraft, rarely using en route control services. 

Similarly, air carrier operators have different operating characteristics than non-air 

carriers. Air carriers generally fly fixed routes, serve large metropolitan airports, 

and have specific time of day requirements. Non-air carriers generally do not 

operate on a fixed schedule and rarely use large primary airports. We found these 

groupings were more meaningful in terms of NAS usage than alternatives such as 

commercial versus recreational aircraft. Either of these groupings (engine or 

operator type) could form the basis for recovering from a group as a whole the 

costs it imposes on FAA. 

M

M

1:A

2:AM

3:A

4:A

5:A

6:AM

7:A

8:AM

9:A

10A

11A

12

1:

2:P

3:

4:P

5:

6:PM

7:

8:P

9:

10P

11

M

M

M

M

M

M

M

PM

PM

M

PM

M

PM

PM

M

PM

M

PM

 12AM 2AM 4AM 6AM 8AM 10AM 12PM 2PM 4PM 6PM 8PM 10PM

public general aviation commercial
17

Fuel Consumption is a Better Measure of Use of the NAS than 

Existing Passenger and Cargo Taxes, but it Does Not Measure the 

Use of Air Traffic Control Services 

Existing passenger and cargo excise taxes have a minimal relationship to the use 

of air traffic control services. Trust Fund revenue generated by the passenger 

ticket taxes and cargo waybill taxes depends on the ticket price or waybill amount 

and the quantity of passengers or cargo on a flight, not the air traffic control 

services received. Thus, there is disparity among the commercial operators 

subject to the excise taxes—the revenue generated by large air carrier aircraft 

versus smaller aircraft operated by air taxis and fractional operators. The 

passenger and cargo excise taxes, which are applied only to commercial flights, 

also create a disparity when compared to the fuel tax paid by general aviation 

users of the same air traffic control services. 

Based on a review of five nonstop markets, a tax based on fuel consumption 

would distribute the fee burden more equitably than the current excise tax system. 

In the markets studied, air carriers accounted for 92 percent of all flight activity, 

but paid 99 percent of the taxes collected under the current system (see table 5). 

The tax share would decline to 97 percent under a fuel only tax (see table 5). Nonair carrier flights, on the other hand, comprised 8 percent of the flight activity and 

contributed only 1 percent under the current tax and fee structure. Under a fuelonly tax system, contributions to the cost of operations by non-air carriers would 

increase to 3 percent. 

Table 5. Fuel Consumption as a Measure of System Use 

 Flight Fuel Consumption and Current Tax Contribution – October 2006

Air Carrier Non-air carrier 

Percent 

of Flights 

Percent of 

Fuel 

Consumed 

Contributions 

Under 

Current Tax 

Percent 

of Flights Market 

Percent of 

Fuel 

Consumed

Contributions 

Under 

Current Tax

Newark – Los Angeles 99.1% 99.5% 99.8% 0.9% 0.5% 0.2% 

Salt Lake City – Seattle 70.4% 82.6% 88.9% 29.6% 17.4% 11.1% 

Memphis – Miami 97.2% 99.3% 99.9% 2.8% 0.7% 0.1% 

Boston – La Guardia 97.6% 99.1% 99.9% 2.4% 0.9% 0.1% 

Las Vegas- Los Angeles 90.6% 94.4% 99.2% 9.4% 

 Source: OIG Analysis of FAA, BTS and DOT Data 

5.6% 0.8% 

Weighted Average 92.3% 96.9% 98.8% 7.7% 3.1% 1.2% 
18

However, a tax based on fuel consumption is not a perfect proxy for NAS activity 

since fuel consumption can vary in proportion to factors unrelated to that activity, 

such as aircraft weight. In addition, fuel consumption neither measures whether 

ATC services are used nor distinguishes among the types and complexity of the 

services used. Similarly, the current ticket, segment, and freight waybill taxes do 

not vary according to the complexity or amount of ATC services consumed. 

In conclusion, we did not find support for the arguments that either piston engine 

airplanes, rotorcraft, or non-air carrier operators are marginal users of the NAS 

and do not contribute to congestion. However, we did find support for the 

argument that these user groups tend to avoid the large primary metropolitan 

airports, particularly when a reliever airport is nearby. We found that both air 

carriers and non-air carriers contribute to congestion at the terminal area radar and 

en route facilities we examined. We also found that user groupings based either 

on aircraft or operator type would provide a more homogeneous grouping of users, 

according to their use of the NAS, than is inherent in the current excise tax 

structure. Finally, we found that a tax based on jet fuel consumption is a better 

proxy for the use of the NAS than the current aviation excise taxes, but it does not 

measure whether air traffic control services are used, nor does it distinguish 

between the types and complexities of services used. 

We met with FAA officials to discuss our results, and their technical comments 

were incorporated into the report. Since we are making no recommendations, no 

formal response to this report is required. We appreciate the courtesies and 

cooperation given by FAA representatives during this audit. If I can be of further 

assistance, please feel free to contact me at (202) 366-1981 or Mitchell Behm, 

Program Director, at (202) 366-1995. 

# 

cc: FAA Assistant Administrator for Aviation Policy, 

 Planning, and Environment 

FAA Chief of Staff 

FAA Audit Liaison 
19

EXHIBIT A. SCOPE AND METHODOLOGY 

Scope 

In a letter to the Inspector General, the House Committee on Transportation and 

Infrastructure, Subcommittee on Aviation requested that our office determine who 

uses the National Airspace System and how users contribute to congestion. In 

addition, we were requested to evaluate whether jet fuel consumption was 

representative of NAS usage. 

Data in this report were obtained from the FAA. The data was used to perform the 

analyses detailed below. 

This performance audit was conducted in accordance with generally accepted

Government Auditing Standards prescribed by the Comptroller General of the 

United States with the exception of the data quality standards described below. 

There has been no prior audit coverage in this area by the Department of 

Transportation’s Office of Inspector General. 

Methodology 

Our analysis focused on the flight activity of FY 2005. It is the latest period for 

which enhanced FAA flight activity data were available. 

We analyzed data on tower, terminal area, and en route air traffic control (ATC) 

operations to assess the use of air traffic control services. We obtained the 

operations data from FAA. We used the data to analyze the use of ATC services 

by aircraft operator type (carrier, non-air carrier, and public user) and by aircraft 

engine type (jet, turboprop, and piston/rotor). The analysis extended to use of ATC 

services at different types of towers and terminal control areas as well as at 

domestic and oceanic en route facilities. For tower facilities, we also conducted 

analyses of operations at individual tower facilities. 

We examined contributions to congested air traffic control services by analyzing 

demand for the largest passenger service airports and several of the most heavily 

used terminal control TRACONs and en route centers. We analyzed demand by 

time of day and by user group. 

The fuel as a proxy analysis was based on flight data obtained using the FAA’s 

ETMSC database for selected origin and destination markets over the period of 

one month (October 2006). 

 

Exhibit A. Scope and Methodology 
20

For each of the markets selected: 

• We utilized Form 41 data to determine fuel burn rates for each of the 

aircraft types (large jets, regional jets, business jets, general aviation 

aircraft, and cargo aircraft). 

• We obtained revenue data from the FAA for cargo carriers, air taxi 

operations, belly cargo on commercial carriers, and fractional and other 

non-scheduled Part 135 passenger and cargo carriers. 

• We utilized the quarterly airfare data for Q106 which is compiled published 

by OST to estimate the average air fares between the selected origin and 

destination markets. 

• We utilized BTS data for estimates of average system-wide load factors. 

Using this information we examined and modeled contributions made by different 

aircraft groups under the current excise tax system compared to a fuel only excise 

tax system and a weight and distance based user fee. 

Data 

We did not systematically audit or validate the data in any of the databases. 

However, in prior work, we conducted trend analyses and checks of the data to 

assess reasonableness and comprehensiveness. We also spoke with managers 

responsible for maintaining the databases to understand any noted inconsistencies 

and attempt to resolve them. Based on our understanding of the data through 

discussions with knowledgeable agency officials, as well as checks for obvious 

errors in accuracy and completeness, we determined that the data was sufficiently 

reliable for our purposes. 

1. Data Package for Stakeholders: FAA-developed air traffic activity data 

and cost accounting data. The air traffic activity measures include 

operations data for FAA towers and approach control facilities and flight 

activity data for domestic and en route flights. The data provide information 

on air traffic activity by user groups (aircraft operator types) and by aircraft 

engine types. In addition, FAA provided individual flight operations 

records for flights at selected TRACONs, towers, and en route centers. 

This data included time of day information. Scope: FY 2005. 

We found that FAA understated piston engine airplane and rotorcraft NAS 

usage in FY 2005 by an estimated 6 percent due to a partial error in its 

Exhibit A. Scope and Methodology 
21

methodology.14 As a result, we believe the actual percent of tower 

operations by piston engine airplanes and rotorcraft was approximately 47 

percent as opposed to the 41 percent FAA reported. Conversely, jet and 

turboprop usage was approximately 53 percent as opposed to the reported 

59 percent. The data did not allow us to restate the jet and turboprop 

categories separately. However, the error does not appear to have a 

significant impact on the results of the FAA cost allocation methodology. 

2. Air Traffic Activity Data System (ATADS): An FAA database of flight 

activity at staffed facilities. Scope: Airport towers across the country, 

FY 2005. 

3. Enhanced Traffic Management System (ETMS): An FAA-maintained 

database providing detailed flight records, including time, distance, aircraft 

types, and user types for aircraft flying under an instrument flight plan. 

Scope: October 2006. 

 

 

14 FAA made an allocation of generic general aviation operations among the different engine type classifications 

without taking into consideration that most general aviation jet and turboprop aircraft were already accounted for in 

another (ETMS) data source, thus creating duplicate counts for many of those types and under counting of piston and 

rotor aircraft operations. 

Exhibit A. Scope and Methodology 
 22 

EXHIBIT B. MAJOR CONTRIBUTORS TO THIS REPORT 

THE FOLLOWING INDIVIDUALS CONTRIBUTED TO THIS REPORT.

Name Title 

David Tornquist Assistant Inspector General for 

Rail and Maritime Program 

Audits and Economic Analysis 

Mitchell Behm Program Director 

Marshall Jackson Project Manager 

Stephen Smith Transportation Industry Analyst 

Ralph W. Morris Economist 

Jay Borwankar Financial Analyst 

Meredith McDaniel Analyst 

Darlisa Crawford Writer-Editor 

 
 23 

The following pages contain textual versions of the charts and graphs found in this 

document. These pages were not in the original document, but have been added 

here to accommodate assistive technology. 

 
 24 

Use of the National Airspace System 

Section 508 Compliant Presentation 

Figure 1. Use of Air Traffic Control Services by Aircraft Type – FY 2005 

Aircraft Type Tower Terminal En Route 

Jet 46% 55% 89% 

Turboprop 13% 14% 7% 

Piston/Rotorcraft 41% 31% 4% 

Figure 2. Use of Air Traffic Control Services by Operator Group – FY 2005 

Operator 

Group 

Tower Terminal En Route 

Carrier 35% 44% 79% 

Non-Air 

Carrier 

59% 49% 17% 

Public 6% 7% 4% 

Figure 3. Jet Use of Air Traffic Control Services – FY 2005 

Operator 

Group 

Tower Terminal En Route 

Carrier 30% 38% 75% 

Non-Air 

Carrier 

12% 13% 11% 

Public 4% 4% 3% 

Figure 4. New York Terminal Control Area – FY 2005 

Arriving Flight Operations by Hour of Day 

(LaGuardia, Newark, and John F. Kennedy Airports) 

Time of Day Air Carrier Operations Non-Air Carrier 

Operations 

7 a.m. 67 2 

8 a.m. 69 2 

9 a.m. 65 2 

10 a.m. 78 3 

11 a.m. 75 3 

12 p.m. 89 2 

1 p.m. 89 3 

2 p.m. 106 3 

 
 25 

3 p.m. 108 3 

4 p.m. 115 4 

5 p.m. 94 3 

6 p.m. 100 3 

7 p.m. 100 2 

Figure 5. New York Terminal Control Area – FY 2005 

Instrument Approach Operations by Hour of Day 

(Includes Outlying Airports) 

Time of Day Air Carrier Operations Non-Air Carrier 

Operations 

7 a.m. 71 19 

8 a.m. 74 27 

9 a.m. 73 29 

10 a.m. 87 33 

11 a.m. 82 36 

12 p.m. 98 38 

1 p.m. 96 39 

2 p.m. 115 42 

3 p.m. 117 46 

4 p.m. 129 50 

5 p.m. 105 53 

6 p.m. 110 48 

7 p.m. 108 40 

Figure 6. En Route Center Operations by Hour of Day 

Cleveland Center – July 2005 

Time of Day Commercial 

Operations 

General Aviation 

Operations 

Public 

Operations 

12 a.m. 75 9 2 

1 a.m. 38 5 2 

2 a.m. 26 3 2 

3 a.m. 28 3 1 

4 a.m. 52 4 1 

5 a.m. 118 8 2 

6 a.m. 237 28 4 

7 a.m. 328 70 7 

8 a.m. 312 95 9 

9 a.m. 392 101 12 

10 a.m. 366 104 13 

11 a.m. 309 93 11 

 
 26 

12 p.m. 366 94 12 

1 p.m. 333 98 12 

2 p.m. 354 103 13 

3 p.m. 423 105 12 

4 p.m. 347 109 11 

5 p.m. 411 96 10 

6 p.m. 359 80 9 

7 p.m. 413 58 9 

8 p.m. 352 47 7 

9 p.m. 335 34 4 

10 p.m. 248 23 4 

11 p.m. 160 15 3 

Note: General Aviation represents between 18 percent and 23 percent of total 

operations during peak hours. 

Figure 7. En Route Center Operations by Hour of Day 

Atlanta Center – July 2005 

Time of Day Commercial 

Operations 

General Aviation 

Operations 

Public 

Operations 

12 a.m. 94 10 3 

1 a.m. 38 6 2 

2 a.m. 16 4 1 

3 a.m. 15 4 1 

4 a.m. 28 5 1 

5 a.m. 70 8 1 

6 a.m. 197 30 1 

7 a.m. 286 83 4 

8 a.m. 346 134 9 

9 a.m. 412 155 20 

10 a.m. 374 151 23 

11 a.m. 403 141 24 

12 p.m. 394 133 24 

1 p.m. 380 133 24 

2 p.m. 371 138 24 

3 p.m. 378 142 24 

4 p.m. 388 142 21 

5 p.m. 401 124 15 

6 p.m. 370 99 13 

7 p.m. 372 72 11 

8 p.m. 330 55 11 

 
 27 

9 p.m. 371 38 8 

10 p.m. 304 27 5 

11 p.m. 193 16 3 

Note: General Aviation represents between 21 percent and 28 percent of total 

operations during peak hours.