Appendix A: Methodology for the 2019 General Aviation

and Part 135 Activity Survey

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APPENDIX A

METHODOLOGY FOR THE 2019 GENERAL AVIATION

AND PART 135 ACTIVITY SURVEY

Purpose of Survey

The General Aviation and Part 135 Activity Survey (GA Survey) provides the Federal Aviation 

Administration (FAA) with information on general aviation and on-demand Part 135 aircraft 

activity. The survey enables the FAA to monitor the general aviation fleet so that it can 

anticipate and meet demand for National Airspace System (NAS) facilities and services, assess 

the impact of regulatory changes on the fleet, and implement measures to assure the safe 

operation of all aircraft in the NAS. The data are also used by other government agencies, the 

general aviation industry, trade associations, and private businesses to identify safety problems 

and to form the basis for research and analysis of general aviation issues.

Background and History

Prior to the first implementation of the annual GA Survey in 1978, the FAA used the Aircraft 

Registration Eligibility, Identification, and Activity Report (AC Form 8050-73) to collect data on 

general aviation activity. The form was sent annually to all owners of civil aircraft in the United 

States and served two purposes: a) Part 1 was the mandatory aircraft registration revalidation 

form; and b) Part 2 was voluntary and applied to general aviation aircraft only, asking questions 

on the owner-discretionary characteristics of the aircraft such as flight hours, avionics 

equipment, base location, and use. The FAA used this information to estimate aircraft activity.

In 1978, the FAA replaced AC Form 8050-73 with a new system. Part 1 was replaced by a 

triennial registration program. In January 1978, the FAA implemented a new procedure, known 

as triennial revalidation, for maintaining its master file. Instead of requiring all aircraft owners to 

revalidate and update their aircraft registration annually, the FAA only required revalidation for 

those aircraft owners who had not contacted the FAA Registry for three years. In 2010, the FAA 

eliminated the voluntary Triennial Aircraft Registration Report Program and established rules 

that require renewal of an aircraft registration every three years and place time-limits on interim 

statuses.1

Part 2 of AC Form 8050-73 was replaced by the General Aviation Activity Survey. Conducted 

annually, the survey was based on a statistically selected sample of aircraft, and it requested

the same type of information as Part 2 of AC Form 8050-73. The first survey took place in 1978

and collected data on the 1977 general aviation fleet. The 2019 statistics in this report are 

based on the 42nd GA Survey, which was implemented in 2020.

2

1 Federal Register Vol 75, No. 138, Tuesday, July 20, 2010, Rules and Regulations, “Re-Registration and 

Renewal of Aircraft Registration.”

2 The name of the survey has changed periodically since 1977. In 1993, the survey was entitled “General 

Aviation and Air Taxi Activity Survey” to reflect the inclusion of air taxi (on-demand Part 135) aircraft. In 

1999, the survey name changed to General Aviation and Air Taxi Activity and Avionics Survey because 

questions about avionics were included every year rather than every other year. Since 2006, the survey 

has been conducted as the General Aviation and Part 135 Activity Survey.
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The GA Survey has undergone periodic revisions to content, implementation, and definition of 

the GA population in order to remain current with regulations, activity patterns, and aviation 

technology. Chapter 1 of this report (“Historical General Aviation and Air Taxi Measures”) 

presents statistical estimates of fleet size and activity for a 10-year period.3 Tables A.1 through 

A.3 summarize changes in survey content and design, data collection methods, sample and 

population definitions that may affect comparability of statistical estimates across surveys. 

Table A.1: Changes in Form or Content of Survey Questionnaire, by Survey Year

Year Change in form or content of survey questionnaire

1993 Added sightseeing and external load to use categories

1996 Added public use (i.e., flights for the purpose of fulfilling a government function) to use 

categories

1999 Re-design the survey form to reduce item non-response, add new content, and be compatible 

with optical scanning

Added air medical services to use categories

Discontinued the “other” use category as used in previous years

Began collecting avionics data every year, rather than every other year

2000 “Public use” asked as a separate question

2002 Use categories refined to be mutually exclusive and exhaustive and match definitions used by 

National Transportation Safety Board for accident reporting

2004 Air medical services was divided into two types to capture air medical flights under Part 135 

and air medical flights not covered by Part 135

A more clearly defined “other” use category was reintroduced

2005 Fractional ownership question was changed from yes/no to a percentage of hours flown

Reduced the number of fuel type response categories by removing obsolete options

Average fuel consumption (in gallons per hour) was added

Revised questions about avionics equipment by adding and rearranging items

2007 Location of aircraft revised to ask the state or territory in which the aircraft was “primarily 

flown” during the survey year rather than where it was "based” as of December 31st of the 

survey year

Percentage of hours flown in Alaska was added

Questions on percentage of hours flown under different flight plans, flight conditions, and 

day/night were revised into a single tabular format

Number of types of landing gear systems was expanded 

Ice protection equipment was revised and prohibition from flight in icing conditions was added

Questions about avionics equipment were revised 

3 Excluding estimates for the 2011 survey year, which are not available. For 2011 GA data, use the FAA 

Aerospace Forecast estimates 

(http://www.faa.gov/data_research/aviation/aerospace_forecasts/media/Tables_28-31.xlsx).
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Year Change in form or content of survey questionnaire

2009 Two questions about avionics equipment were revised:

“Air Bag/Ballistic Parachute” was asked as two items—“Air Bag” and “Ballistic 

Parachute”

“ADS-B (Mode S)” was separated into two questions—“ADS-B (Mode S) Transmit 

Only (Out)” and “ADS-B (Mode S) Transmit and Receive (In)”

2010 Removed the skip instruction in the mail survey based on responses to Part 121/129 

operations

Added “Specify” option if reason not flown was “Other”

2013 Added “Specify” option if fuel type was “Other”

Added response categories for reason not flown (“Under maintenance or repair,” “Parted 

out/salvaged,” and “In storage”)

The text “Corporate/Executive Transportation” was removed from the description of this use 

category and replaced with “Business Transportation – (with a paid flight crew).” The 

definition of this use is unchanged.

2014 Added response category for kind/grade of fuel primarily used (”Propane/LP Gas”)

2016 The following questions on the 2016 full survey form underwent additions, deletions, and text 

changes: 

• Reason not flown

• Percentage of total hours flown under fractional ownership

• Percentage of total hours flown under filed flight plans

• Fuel type

• Avionics.

Other questions and response categories were re-ordered. Data end-users should consult the 

survey documents in Appendix B of the current and previous year’s survey report.

2019 Eliminated non-mutually exclusive transponder selection options in “Installed 

Transponder/Surveillance Equipment” section of avionics questions
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Table A.2: Changes in Data Collection Methodology, by Survey Year

Year Change in data collection methodology

1999 Non-respondent telephone survey conducted to adjust active aircraft and hours flown 

estimates4

2000 Discontinued non-respondent telephone survey Added Internet response option

2003 Added a reminder/thank-you postcard between the first and second mailings

2004 Introduced “large fleet” summary form for owners/operators of multiple aircraft Initiated 

telephone follow-up effort to contact owners/operators of multiple aircraft who had not 

responded. 

2010 Introduced end-of-field-period follow-up postcard to owners/operators of single aircraft that 

participated the previous survey year but had not yet completed the current year’s survey

2014 Introduced use of email to invite sampled aircraft owners/operators to complete the survey

Table A.3: Changes in Sample Design or Definition of Survey Population, by Survey Year

Year Change in sample design or survey population

1993 Number of aircraft types classified by the sample was expanded from 13 to 19

1999 Sample design revised to stratify by aircraft type and FAA region 5

2003 Aircraft with known incorrect addresses and identified as “Postmaster Return” status on the 

Registry were retained in the definition of the survey population and eligible for sample

selection 

2004 Aircraft listed on the Registry as “registration pending” or “sold” (if sold status less than five

years ago) were retained in the definition of the survey population and eligible for sample 

selection. Sample design revised to stratify by aircraft type, FAA region, and whether the 

aircraft is certified to fly Part 135. Introduced 100 percent samples of turbine aircraft, 

rotorcraft, on-demand Part 135, and Alaska-based aircraft

2005 Introduced light-sport aircraft as an aircraft type sampled at 100 percent. Light-sport included 

aircraft with special or experimental airworthiness as well as aircraft for which airworthiness 

was not yet final.

2006 Sample design simplified to fewer aircraft types and included 100 percent sample of aircraft 

manufactured in the past five years

2008 100 percent sample of light-sport aircraft was limited to special light-sport aircraft. 

Experimental light-sport and light-sport without completed airworthiness sampled at a rate 

less than 1.0.

2010 Aircraft excluded from the survey population if “sale reported” or “registration pending” more 

than 12 months. These aircraft no longer eligible for sample selection due to implementation 

of the re-registration rule.

2012

Aircraft excluded from the survey population if registration was expired. These aircraft no 

longer eligible for sample selection because they do not have valid registrations due to 

implementation of the re-registration rule.

Unmanned aerial vehicles are excluded from the survey population.

4 Telephone surveys of non-respondents also were conducted in 1977, 1978, 1979, 1997, and 1998. 

Please refer to the 1999 GA Survey report for a full discussion of the telephone survey of nonrespondents.

5 Before 1999, the sample was stratified by aircraft type and state/territory.
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Survey Population and Survey Sample

The survey population for the 2019 General Aviation and Part 135 Activity Survey includes all 

civil aircraft registered with the FAA that are based in the US or US territories and that were in 

existence, potentially active between January 1 and December 31, 2019, and had a valid 

registration. This includes aircraft operating under:

• Part 91: General operating and flight rules

• Part 125: Certification and operations: Airplanes having a seating capacity of 20 or 

more passengers or a maximum payload capacity of 6,000 pounds or more (but not 

for hire)

• Part 133: Rotorcraft external load operations

• Part 135: On-demand (air taxi) operations 

• Part 137: Agricultural aircraft operations.

Aircraft operating under Part 121 as defined in Part 119 are excluded from the survey 

population. Foreign air carriers, which operate under Part 129, are also not part of the survey 

population. Civil aircraft that are known not to be potentially active during the survey year are 

excluded from the population (e.g., aircraft on static display, destroyed prior to January 1, 2019).

The Aircraft Registration Master File, maintained by the FAA’s Mike Monroney Aeronautical 

Center in Oklahoma City, Oklahoma, serves as the sample frame or list of cases from which a 

sample of civil aircraft is selected. The Registration Master File (“Registry”) is the official record 

of registered civil aircraft in the United States. For the purpose of defining the 2019 survey 

population, we used the Registry’s list of aircraft effective through December 31, 2019.

6

The Registry, like many sample frames, is an imperfect representation of the survey population. 

While it may exclude a small number of aircraft that operate under the FAA regulations 

governing the operation of general aviation and on-demand Part 135 aircraft, it also includes 

aircraft that are not part of the survey population. Prior to sample selection, the following 

ineligible aircraft are removed: Aircraft whose registration has been cancelled or revoked

• Aircraft based in Europe or registered to a foreign company that has not returned 

flight hour reports

• Aircraft that operate under Part 121

• Aircraft destroyed or moved to static display prior to January 1, 2019

6 The Civil Aviation Registry updates the Master file approximately weekly but not on a schedule that 

corresponds exactly to December 31st. For the 2019 survey population, we used a Registry Master file 

that was made available on January 22, 2020, and reflected records processed through December 30, 

2019.
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• Aircraft that are flagged Postmaster Return (known to have incorrect address 

information) on the aircraft Registration file prior to 2010 (ten years prior to survey 

year).

• Aircraft that have held interim registration statuses (e.g., “sale reported”) more than 

more than 12 months (prior to January 1, 2019)

7

• Aircraft with registrations that expired prior to January 1, 2019

• Aircraft that are unmanned aerial vehicles.

The Registry Master file used to define the 2019 survey population included 289,755 aircraft. 

This represents a decrease of 1.4 percent compared with the Registry file from 2018 (293,841). 

After excluding the aircraft described above, 272,554 records remain, which is 94 percent of the 

Registry. The 2019 survey population of 272,554 is a decrease of 77 aircraft compared to the 

2018 population of 272,631 aircraft.

The 2019 GA Survey Sample

The 2019 survey sample is stratified by aircraft type, FAA region in which the aircraft is 

registered, whether the aircraft operates under a Part 135 certificate, and whether the aircraft 

was manufactured in the past five years. Aircraft operated under a Part 135 certificate were 

identified using the FAA’s Operations Safety System (OPSS) database that was merged with 

the Registry by N-number. 

Aircraft are classified into FAA regions by the state or US territory of registration. Table A.4

summarizes how states and territories are mapped to region.8

7 The registration rule allows aircraft to be listed as sale reported for a maximum of six months. For the 

purpose of defining the survey population, we allow aircraft to hold this status for 12 months because we 

cannot consistently differentiate among aircraft that did or did not hold valid statuses for the other six 

months of the year. The number of aircraft mistakenly included in the survey population should be small. 

The error of including ineligible aircraft has a smaller impact on statistical estimates of activity than 

erroneously excluding eligible and potentially active aircraft.

8 The FAA defines the regions at www.faa.gov/about/office_org/headquarters_offices/arc/ro_center. 

Statistical estimates reported by region in which an aircraft is primarily flown follow the same mapping 

based on the state in which the aircraft is primarily operated.
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Table A.4: Regions and States/Territories Constituting Region

Region States/Territories

Alaska Alaska

Central Iowa, Kansas, Missouri, Nebraska

Eastern Delaware, Maryland, New Jersey, New York, Pennsylvania, Virginia, Washington, 

D.C., West Virginia

Great Lakes Illinois, Indiana, Michigan, Minnesota, North Dakota, Ohio, South Dakota, 

Wisconsin

New England Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont

Northwest Mountain Colorado, Idaho, Montana, Oregon, Utah, Washington, Wyoming

Southern Alabama, Florida, Georgia, Kentucky, Mississippi, Navassa Island, North 

Carolina, Puerto Rico, South Carolina, Tennessee, US Virgin Islands

Southwestern Arkansas, Louisiana, New Mexico, Oklahoma, Texas

Western-Pacific American Samoa, Arizona, Baker, Howland, and Jarvis Islands, California, Guam, 

Hawaii, Johnston Atoll, Kingman Reef, Midway Islands, Nevada, Palmyra Atoll, 

Wake Island

We define 15 aircraft types to execute the sample design. The classification distinguishes 

among fixed wing aircraft, rotorcraft, experimental aircraft, light-sport, and other aircraft. Within 

the major categories of fixed wing and rotorcraft, we differentiate aircraft by type and number of 

engines (e.g., piston, turboprop, turbojet, turbine, single- and two-engines). Experimental aircraft 

are subdivided by amateur-built status and airworthiness certification, and we classify “other” 

aircraft as gliders or lighter-than-air. Light-sport is subdivided into special and experimental 

based on airworthiness certification. Light-sport aircraft for which airworthiness certificates are 

not yet final are included with experimental light-sport.

Aircraft Sampled at 100 Percent

The 2019 survey sample includes several types of aircraft that are sampled at a rate of 1.0. 

Because of the FAA’s interest in better understanding the operation of these aircraft, all such 

aircraft listed in the Registry are included in the survey sample to ensure a sufficient number of 

responses to support analysis and provide more precise estimates of fleet size and aircraft 

activity. These include:

• 100 percent sample of turbine aircraft (turboprops and turbojets)

• 100 percent sample of rotorcraft

• 100 percent sample of special light-sport aircraft

• 100 percent sample of aircraft operating on-demand Part 135 

• 100 percent sample of aircraft registered in Alaska

• 100 percent sample of aircraft manufactured within the past five years (since 2015

inclusive).
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Aircraft sampled at 100 percent account for 59,124 observations in the 2019 survey sample. 

Aircraft Sampled at Less than 100 Percent

Aircraft that are not part of a 100 percent sample are selected based on sampling fractions 

defined for each cell in the sample design matrix. Flight hours is the primary measure needed 

by the FAA. Sample fractions for each sample strata are defined to optimize sample size to 

obtain a desired level of precision for an estimate of flight activity. Data from the previous survey 

year on average hours flown, variability in hours flown by region and aircraft type, and response 

rates are used to set precision levels and target sample sizes for each stratum. Aircraft are 

randomly selected from each cell in the matrix, subject to the desired sample size. Strata where 

the desired sample size exceeds the population are examined and the sample size is adjusted 

to include all observations.9 The 2019 survey sample includes 25,870 aircraft that are selected 

at a rate of less than 1.0, which is a decrease from 2018 when 26,707 aircraft were sampled.

The 2019 GA Survey sample included 84,994 aircraft. Table A.5 summarizes the population 

counts and sample sizes by aircraft type.

9

In 2019, an additional six strata were sampled at 100 percent to meet precision requirements (1,406

aircraft).
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Table A.5: Population and Survey Sample Counts by Aircraft Type

Aircraft Type Population Sample Size

Sample as 

Percent of 

Population

Fixed Wing - Piston 179,881 31,380 17.4

1 engine, 1–3 seats 50,605 6,898 13.6

1 engine, 4+ seats 113,369 15,314 13.5

2 engines, 1–6 seats 11,269 6,332 56.2

2 engines, 7+ seats 4,638 2,836 61.1

Fixed Wing - Turboprop 11,064 11,064 100.0

1 engine 5,537 5,537 100.0

2 engines, 1–12 seats 3,917 3,917 100.0

2 engines, 13+ seats 1,610 1,610 100.0

Fixed Wing - Turbojet 15,985 15,985 100.0

Rotorcraft 12,197 12,197 100.0

Piston 4,133 4,133 100.0

Turbine (1 engine) 5,904 5,904 100.0

Turbine (multi-engine) 2,160 2,160 100.0

Other Aircraft 7,181 2,113 29.4

Glider 2,742 851 31.0

Lighter-than-air 4,439 1,262 28.4

Experimental 43,202 9,211 21.3

Amateur 32,796 5,248 16.0

Exhibition 3,033 1,448 47.7

Experimental light-sport* 6,251 1,485 23.8

Other experimental 1,122 1,030 91.8

Special light-sport 3,044 3,044 100.0

Total 272,554 84,994 31.2

* Includes light-sport aircraft with experimental airworthiness and light-sport aircraft for which airworthiness 

certification is not final

Weighting the Survey Data

Data from completed surveys are weighted to reflect population characteristics. The weights 

reflect the proportion of aircraft sampled from the population in each sample strata and 

differential response as well as adjustment for aircraft that are not part of the survey population.
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Initially, each aircraft for which we receive a completed survey is given a weight that reflects 

sampling fraction and differential response. That is:

WEIGHT = (Population Nijkl/Sample Nijkl) * (Sample Nijkl/N Respondentsijkl)

where i, j, k, and l represent the four sample strata of aircraft type, FAA region, Part 135 status, 

and whether an aircraft was manufactured in the past five years.

The weight is subsequently adjusted to reflect information about non-general aviation aircraft. 

Survey responses that indicate an aircraft is not part of the survey population—e.g., destroyed 

prior to January 1, 2019; displayed in a museum; or operated primarily under Part 121 or 129—

are used to remove aircraft from the sample and the population. The procedure assumes that 

ineligible aircraft occur similarly among survey respondents and non-respondents. To the extent 

that ineligible aircraft are less likely to receive and complete a survey, this approach will 

underestimate the adjustment for aircraft that are not part of the general aviation population.

Errors in Survey Data

Errors associated with survey data include sampling and non-sampling errors. Sampling errors 

occur because the estimates are based on a sample of aircraft rather than the entire population

and we can expect, by chance alone, that some aircraft selected into the sample differ from 

aircraft that were not selected.

Non-sampling errors include a) errors that arise from difficulties in the execution of the sample 

(e.g., failing to obtain completed interviews with all sample units), and b) errors caused by other 

factors, such as misinterpretation of questions, inability or unwillingness to provide accurate 

answers, or mistakes in recording or coding data.

Sampling Error

The true sampling error is never known, but in a designed survey we can estimate the potential 

magnitude of error due to sampling. This estimate is the standard error. The standard error 

measures the variation that would occur among the estimates from all possible samples of the 

same design from the same population.

This publication reports a standard error for each estimate based on survey sample data. An 

estimate and its standard error can be used to construct an interval estimate (“confidence 

interval”) with a prescribed level of confidence that the interval contains the true population 

figure. In general, as standard errors decrease in size we say the estimate has greater precision 

(the confidence interval is narrower), while as standard errors increase in size the estimate is 

less precise (the confidence interval is wider). Table A.6 shows selected interval widths and 

their corresponding confidence.
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Table A.6: Confidence Interval Estimates

Width of interval

Approximate 

confidence

that interval includes

true population value

1 Standard error 68%

2 Standard error 95%

3 Standard error 99%

This report presents a “percent standard error” for each estimate, which is the standard error 

relative to the mean. The percent standard error is the ratio of the standard error to its estimate 

multiplied by 100. For example, if the estimate is 4,376 and the standard error is 30.632, then 

the percent standard error is (30.632/4,376) x 100 = 0.7. Reporting percent standard errors 

makes it possible to compare the precision of estimates across categories.

Estimates and percent standard errors reported in Table 2.1 in Chapter 2 ("Population Size, 

Active Aircraft, Total Flight Hours, and Average Flight Hours by Aircraft Type") provide an 

example of how to compute and interpret confidence intervals. To obtain a 95 percent 

confidence interval for the estimated number of total hours flown for twin-engine turboprops in 

2019, where the total hours flown is estimated to be 1,178,429 and the percent standard error of 

the estimate is 1.8, the following computation applies:

Lower confidence limit: 1,178,429 – 1.96(1.8/100)(1,178,429) = 1,136,854

Upper confidence limit: 1,178,429 + 1.96(1.8/100)(1,178,429) = 1,220,004

In other words, if we drew repeated samples of the same design, 95 percent of the estimates of 

the total hours flown by twin-engine turboprops would fall between 1,136,854 and 1,220,004.

Non-sampling Error

Sampling error is estimable and can be reduced through survey design (e.g., by increasing 

sample size), but it is difficult, if not impossible, to quantify the amount of non-sampling error. 

Although extensive efforts are undertaken to minimize non-sampling error, the success of these 

measures cannot be quantified.

Steps taken to reduce non-sampling error include strategies to reduce non-response and efforts 

to minimize measurement and coding errors. The 2019 GA Survey incorporated the following 

steps to maximize cooperation among sample members:

• Two methods for completing the survey (Internet, paper-pencil mail form) and three 

methods of inviting survey participation (mail, email, and telephone).

• Three mailings of the survey, reminder letters and postcards, and end-of-field-period 

follow-up postcard or email.

• Cover letters accompanying each survey mailing explained the purpose of the survey 

and the endorsement (organizational logos) of several aviation associations.
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• Cover letters assured owners of the confidentiality of their responses and informed 

them: “Names of individuals are never associated with responses. There is an 

identification number on your survey only so [survey contractor] knows who should 

receive the letter.”

• Use of additional sources to obtain updated contact information and help ensure the 

mail survey reaches the sample member (e.g., National Change of Address).

• Use of a toll-free telephone number and email address to respond to questions.

• Collaboration with aviation organizations and industry groups to raise awareness of 

the survey and encourage cooperation.

• Telephone follow-up to owners or operators of multiple aircraft who had not yet 

responded.

The survey efforts minimize measurement error by increasing the likelihood that respondents 

share a common understanding of survey questions and reducing errors in data coding. These

efforts include:

• Close collaboration with the FAA, other federal agencies, and aviation groups to 

refine question wording and definitions to questions. The questionnaire is reexamined regularly to identify ambiguities or revisions necessary to remain 

consistent with aviation regulations and definitions.

• Periodic re-design of the survey questionnaire and pre-testing significant revisions 

with a sample of aircraft owners or operators. 

• Comprehensive editing and verification procedures to ensure the accuracy of data 

transcription to machine-readable form.

• Manual review and verification of a subset of single-aircraft mail surveys throughout 

the field period.

• Programmed logic checks for web surveys to identify illogical, unusual or 

inconsistent data.

• Analysis of preliminary data to identify unusual or illogical values and place follow-up 

inquiries with participants to verify or correct responses.

We undertake extensive effort to reduce measurement error, particularly where we can 

anticipate systematic or repeated error on the part of survey respondents, but it is impossible to 

eliminate all measurement error. Survey participants may misunderstand questions or misreport 

flight activity in ways that cannot be anticipated or prevented through survey design. Where 

survey reports appear nonsensical or contradict FAA regulations, we manually verify that the 

data were processed accurately. Instances in which a small number of illogical reports occur 

may be suppressed and are indicated in table notes. No additional steps are taken to cleanse 

the data of apparently illogical reports or assign them to other categories. To do so would 

introduce additional and systematic error that would be misleading and would affect other uses 

of the data.
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Imputation of Missing Data

Imputation of missing data is important for stabilizing the estimates of aircraft activity and 

equipment. Values are imputed for variables if the survey response is incomplete, the survey 

form did not include the question, or the Registry data field is blank. Table A.7 lists the variables 

for which values are imputed, describes the imputation procedure, and shows the percentage of 

cases with imputed data. The table shows rates of imputation among active aircraft that 

received the full survey form (first column of numbers) and rates including active aircraft that 

completed the short form (last column).10 Asterisks note the questions not asked on the short 

form. 

Table A.7: Variables with Imputed Values, Imputation Procedure, and Percentage Imputed

Among Active Aircraft

Variable Imputation Procedure

Percent 

Imputed 

(full 

survey 

form only)

Percent 

Imputed (incl. 

short form)

Hours by use (e.g., 

personal, business 

transport)

Mean values by aircraft type 0.8 2.2

Fractional ownership 

hours11

Nearest neighbor by aircraft type 

by make model series

23.9 18.0

Hours rented/leased * Nearest neighbor by aircraft type 

by make model series

1.7 37.2

Public use hours Nearest neighbor by aircraft type 

by make model series

1.5 6.7

Hours by flight 

plans/flight conditions *

Mean values by aircraft type 2.9 38.0

Airframe hours * Nearest neighbor by aircraft type 

by hours flown

5.5 39.6

Number of landings Nearest neighbor by aircraft type 

by make model series by age

2.4 8.5

Landing gear * Nearest neighbor by aircraft type 

by make model series

2.5 37.7

Fuel type * Nearest neighbor by aircraft type 

by make model series

2.5 37.6

Fuel burn rate Nearest neighbor by aircraft type 

by make model series

3.5 5.5

10 The “full” and “short” forms of the survey are described below in the section “Data Collection Methods.”

11 Beginning with the 2016 survey, fractional ownership was no longer asked on the full survey form, 

thereby increasing the imputation rate among full survey returns.
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Variable Imputation Procedure

Percent 

Imputed 

(full 

survey 

form only)

Percent 

Imputed (incl. 

short form)

Avionics equipment * Nearest neighbor by aircraft type 

by make model series by age

9.1 39.7

State primarily flown Assign state of registration from 

Registry 

2.2 14.0

Year of manufacture 

(Registry data field)

Nearest neighbor by aircraft type 

by make model series

0.6 1.5

Percentages are based on unweighted survey responses among active aircraft (total 30,591).12

* Question not asked on the abbreviated survey form administered to owners/operators of multiple aircraft.

In 2019, rates of imputations for most variables are 1 to 5 percent for aircraft that completed the 

full survey form. Item non-response on key activity variables is low—hours flown by use (0.8

percent), rented or leased hours (1.7 percent), and year of manufacture (0.6 percent).

Survey Content

The 2019 GA Survey questionnaire requests the aircraft owner or operator to provide 

information on flight activity, flight conditions, where the aircraft was flown, and aircraft 

characteristics. Variables derived from the survey responses include:

• Number of total hours flown in 2019, hours flown by use, and total lifetime airframe 

hours

• The state in which the aircraft was primarily flown 

• Hours flown by filed flight plan, including flight under Visual Flight Rules (VFR), 

Instrument Flight Rules (IFR), and without flight plans

• Hours flown as part of a fractional ownership program (short form only), rented or 

leased, or used to fulfill a government function

• Type of landing gear and number of landings in 2019

• Fuel type and average fuel burn rate

• Avionics equipment installed in the aircraft.

12 In previous survey years, the imputation rates were calculated based on all survey responses (active 

and inactive aircraft). The rates shown here will not be comparable to those reported in previous years.
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Data Collection Methods

Collecting Data from Owners/Operators of a Single Aircraft

Appendix B presents the materials used to conduct the 2019 survey. The survey form 

administered to owners/operators of a single aircraft is shown in Figure B.1. The postcard 

invitation to the Internet component and the reminder/thank-you postcard are shown in Figures

B.2 and B.3. Surveys sent to aircraft owners who started, but did not complete, an Internet 

survey included a special insert (Figure B.4). Surveys mailed to Alaskan addresses included an 

insert with the endorsement of Alaska aviation associations encouraging owners to participate 

(Figure B.5). Each of the three mailings for the survey was accompanied by a cover letter, 

shown respectively in Figures B.6, B.7, and B.8. The data collection effort for the 2019 survey 

also included an end-of-field-period postcard or email (Figure B.9).

The survey data were collected from owners and operators of the sampled aircraft through two 

modes—the Internet and mailings of the questionnaire. We implemented the Internet 

component before the mailing portion to maximize the number of responses collected 

electronically. We first sent the owners/operators of sampled aircraft a postcard (mailed on 

February 21, 2020) or email (sent February 24, 2020) inviting them to complete the survey on 

the Internet. All single-aircraft surveys received through July 20 (on-line or by mail) were 

processed and included in analysis.

We mailed survey questionnaires to owners/operators of sampled aircraft three times during the 

field period as well as a reminder/thank-you postcard between the first and second mailings and 

an end-of-field-period follow-up postcard. With the exception of the final postcard, each mailing 

was sent to owners or operators who had not yet responded to the survey at that time or had 

not been assigned a final disposition. The final postcard was sent only to owners/operators that 

had participated in the 2018 survey but had not yet completed a 2019 survey by the end of May. 

We mailed the first questionnaire on March 20, 2020, followed by the reminder/thank-you 

postcard on April 17, 2020. The second mailing was sent April 24, 2020. The final postcard was 

mailed on May 29, 2020, prior to the third mailing, which was sent June 5, 2020.

Collecting Data from Owners/Operators of Multiple Aircraft

The 2019 GA Survey continued the effort initiated in 2004 to increase cooperation among 

respondents who own or operate multiple aircraft. The 2019 survey employed data collection 

tools and methods similar to those introduced in 2004, including telephone contact with 

owners/operators of multiple aircraft to encourage participation among non-responders after the 

first mailing. The survey forms, cover letters, and reminder letter are presented in Appendix B, 

Figures B.10–B.14.

The responses of multiple-aircraft owners or operators are important for accurately estimating 

general aviation activity. Because of the increased burden of reporting for multiple aircraft, there 

was a concern that these operators were less likely to respond to the survey. After selecting the 

sample, we identify groups of aircraft belonging to the same operator using several resources: 

FAA’s OPSS, databases available from aviation associations, and the Registry. 

Owners or operators of multiple aircraft receive an abbreviated survey form to minimize the 

reporting burden. The form, developed in cooperation with several aircraft operators and 

aviation associations, allows an operator to report a summary of activity for a group of aircraft of 

a similar type instead of requiring the operator to complete a separate and longer questionnaire 
Appendix A: Methodology for the 2019 General Aviation

and Part 135 Activity Survey

A-16

for each individual aircraft. This survey form (Figure B.10) collects data on key variables for 

major classes of aircraft (e.g., hours flown, how flown, fuel consumption, fractional ownership, 

and number of landings). The form does not collect data on flight plans, fuel type, landing gear, 

or avionics.

Data collection for owners or operators of multiple aircraft followed similar timing as that for 

single aircraft. We programmed an Internet survey that matched the hard-copy survey form and 

the on-line survey remained open throughout the field period. We mailed survey questionnaires 

three times during the field period and sent a reminder letter between the first and second 

mailings. Each mailing was sent to owners or operators of multiple aircraft who had not yet 

responded to the survey and had not been assigned a final disposition. The first survey mailing 

was sent February 21, 2020, followed by a reminder letter on March 27, 2020. The second and 

third mailings were sent April 3, 2020, and June 5, 2020, respectively. All large fleet surveys 

received through July 20 were processed and included in analysis. 

To maximize survey response, we placed follow-up telephone calls to multiple-aircraft owners or 

operators who had not responded. The telephone effort began March 16, 2020 and continued

through the field period. The calling effort focused on encouraging survey participation and

ensuring that survey mailings were reaching the appropriate person in the organization, but 

surveys were completed by telephone when necessary. 

The alternate survey form for owners or operators of multiple aircraft has reduced respondent 

burden and improved representation of activity among high-end and high-use aircraft. In 2019, 

31.2 percent of all completed surveys followed this data collection track.

Response Rate

The response rate is calculated conservatively following guidelines published by the American 

Association for Public Opinion Research (AAPOR), a professional association that establishes 

standards, best practice guidelines, and a code of ethics for professional survey researchers 

and research firms.13 Specifically, the response rate is computed as the number of completed 

and partial surveys returned divided by the total number of eligible aircraft in the sample using 

the following formula. 

RR = (C + P) / (C + P) + (NR + INS + REF + PMR + UNK)

Where

RR = Response Rate

C = Completed survey

P = Partial survey 

NR = No response 

13 The American Association for Public Opinion Research. 2016. Standard Definitions: Final Dispositions 

of Case Codes and Outcome Rates for Surveys. 9th edition. AAPOR.
Appendix A: Methodology for the 2019 General Aviation

and Part 135 Activity Survey

A-17

INS = Insufficient complete; a partial survey that is not sufficient to count as a complete

REF = Refused

PMR = Postmaster Returned, no new address

UNK = Unknown eligibility

The numerator is comprised of completed surveys and partial surveys that provide enough 

information to be used for analysis. Partial surveys must include information on hours flown to 

be analyzed.

In addition to completed and partial surveys, the denominator includes cases for which no 

response was received, insufficiently completed surveys, refusals, surveys returned as 

undeliverable by the US Postal Service, and cases of unknown eligibility. The last category 

includes aircraft in which the owners cannot be identified or cannot report about aircraft activity 

(e.g., owner is deceased, and the survivors cannot report on the aircraft activity, survey recipient 

does not own the aircraft listed).

The denominator includes aircraft that were sold or destroyed during the survey year. The 

survey collects data on flight activity for the portion of the year the aircraft was eligible to fly, and 

data collection efforts attempt to identify and mail surveys to new owners.

The denominator excludes aircraft known not to be part of the general aviation fleet or known 

not to be eligible to fly during the survey year. These are aircraft that were destroyed prior to the 

survey year, operated primarily as an air carrier, operated outside the US, or exported overseas.

Table A.8 shows the final response rate by mailing and overall, along with the number of 

completed surveys. The number of completed surveys shown here excludes duplicate surveys 

after cleaning the returned survey data to retain the form with the most complete information.

The overall response rate for the 2019 GA Survey was 41.4 percent. Over 72 percent of 

responses were received on the Internet and 17 percent were received from the first mailing. 

The second and third mailings had lower response, but these rates are calculated 

conservatively. For example, the Mail 3 response rate is the proportion of sampled aircraft that 

returned that hard-copy survey. If a third mailing was sent, but the survey was later completed 

on-line, then the response is recorded as “Internet.”

Table A.8: Response Rate by Mailing

Mailing Completes

Response 

Rate

% Total 

Response

Internet 25,123 29.9% 72.2%

1

st Mailing 5,724 6.8% 16.5%

2

nd Mailing 2,521 3.0% 7.2%

3

rd Mailing 1,424 1.7% 4.1%

Overall 34,792 41.4% 100.0%
Appendix A: Methodology for the 2019 General Aviation

and Part 135 Activity Survey

A-18

The response rate calculation retains all non-responding surveys, sampled units with bad 

addresses, and sampled aircraft of unknown eligibility in the denominator. In the 2019 survey 

the survey sample included about 754 aircraft that could not be contacted because their status 

was “Sale Reported,” “Registration Pending,” or the address was known to be incorrect based 

on the Registry status. 

Table A.9 shows response rates by aircraft type. The overall response rate in 2019 is 41.4

percent. Participation is highest among experimental amateur aircraft (54 percent), multi-engine 

turbine rotorcraft (53 percent), and experimental light-sport aircraft (52 percent). Piston rotorcraft 

have the lowest rates of participation (32 percent). 
Appendix A: Methodology for the 2019 General Aviation

and Part 135 Activity Survey

A-19

Table A.9: Response Rate by Aircraft Type

Aircraft Type Sample

Invalid 

Sample14 Completes

Response 

Rate

Fixed Wing - Piston 31,380 231 13,510 43.4%

1 engine, 1–3 seats 6,898 39 2,905 42.4%

1 engine, 4+ seats 15,314 57 7,143 46.8%

2 engines, 1–6 seats 6,332 75 2,503 40.0%

2 engines, 7+ seats 2,836 60 959 34.5%

Fixed Wing - Turboprop 11,064 118 4,076 37.2%

1 engine 5,537 18 2,325 42.1%

2 engines, 1–12 seats 3,917 83 1,126 29.4%

2 engines, 13+ seats 1,610 17 625 39.2%

Fixed Wing - Turbojet 15,985 285 5,087 32.4%

Rotorcraft 12,197 138 5,175 42.9%

Piston 4,133 35 1,315 32.1%

Turbine: 1 engine 5,904 55 2,747 47.0%

Turbine: Multi-engine 2,160 48 1,113 52.7%

Other Aircraft 2,113 11 974 46.3%

Glider 851 2 424 49.9%

Lighter-than-air 1,262 9 550 43.9%

Experimental 9,211 72 4,529 49.6%

Amateur 5,248 36 2,791 53.5%

Exhibition 1,448 12 570 39.7%

Experimental light-sport* 1,485 8 761 51.5%

Experimental Other 1,030 16 407 40.1%

Special light-sport 3,044 17 1,441 47.6%

Total 84,994 872 34,792 41.4%

* Experimental light-sport includes aircraft with experimental airworthiness certification and light-sport 

aircraft for which airworthiness certificates are not final.

14 We remove non-GA aircraft from the population before the sample is selected, but some surveys are 

returned indicating that the aircraft should not be part of the survey population (e.g., the aircraft was 

destroyed or salvaged, placed on static display, used only in ground maintenance school training). The 

Invalid Sample represents such aircraft, which are excluded from response rate calculations.