**APPENDIX A**

**METHODOLOGY FOR THE 2004 GENERAL AVIATION AND AIR TAXI ACTIVITY AND
AVIONICS (GAATAA) SURVEY**

**Purpose of Survey**

The purpose of the GAATAA Survey is to provide the Federal Aviation
Administration (FAA) with information on general aviation and on-demand
Part 135 aircraft activity. The information obtained from the survey
enables the FAA to monitor the general aviation fleet so that it can,
among other activities, 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 NAS. The data collected are also used by
other government agencies, the general aviation industry, trade
associations, and private businesses to pinpoint safety problems and to
form the basis for critical research and analysis of general aviation
issues.

**Background and History**

Prior to the first implementation of the annual GAATAA 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: (1) Part 1 was the mandatory
aircraft registration revalidation form, and (2) 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. This less frequent updating of the
master file affected its accuracy and representativeness:

> 1\. The accuracy of current owners and their addresses deteriorated.

2\. The master file combined a residue of aircraft, which under the old
revalidation system would have been reregistered and purged from the
file, but now remain under the new system.

Part 2 of AC Form 8050-73 was replaced by the General Aviation Activity
(GAA) Survey. Conducted annually, the survey is based on a statistically
selected sample of aircraft, and it requests the same type of
information as Part 2 of AC Form 8050-73. The first GAA Survey took
place in 1978, collecting data on the 1977 general aviation fleet.

In 1993, the name of the GAA Survey was changed to the General Aviation
and Air Taxi Activity (GAATA) Survey to reflect that the survey includes
air taxi (that is, on-demand Part 135) aircraft. Starting in 1999, the
avionics section, which was previously included only every other year,
was asked every year. As a result, the survey's name was changed to the
General Aviation and Air Taxi Activity and Avionics (GAATAA) Survey.
This is the name under which the 2004 survey was conducted.

The GAATAA Survey has undergone periodic revisions to content,
implementation, and definition of the GA population in order to remain
current with regulations, activity patterns, and general aviation
community. The table below summarizes changes in survey content.

+-----+----------------------------------------------------------------+
| **  | **Description of change to survey content**                    |
| Yea |                                                                |
| r** |                                                                |
+-----+----------------------------------------------------------------+
| 1   | Added sightseeing and external load to use categories          |
| 993 |                                                                |
+-----+----------------------------------------------------------------+
| 1   | Added public use (i.e., flights for the purpose of fulfilling  |
| 996 | a government function) to use categories                       |
+-----+----------------------------------------------------------------+
| 1   | Significant re-design of the entire survey form to reduce item |
| 999 | non-response, add new content, and be compatible with optical  |
|     | scanning                                                       |
|     |                                                                |
|     | Added air medical services to use categories                   |
|     |                                                                |
|     | Discontinued the use of a catch-all 'other' category as used   |
|     | in previous years                                              |
|     |                                                                |
|     | Began collecting avionics data every year, rather than every   |
|     | other year                                                     |
+-----+----------------------------------------------------------------+
| 2   | Public use asked as a separate question, independent of other  |
| 000 | use categories (e.g., personal/recreation, business            |
|     | transportation), because it was not mutually exclusive with    |
|     | respect to other flight activity                               |
+-----+----------------------------------------------------------------+
| 2   | Use categories refined to be mutually exclusive and exhaustive |
| 002 | and match definitions used by NTSB for accident reporting      |
+-----+----------------------------------------------------------------+
| 2   | Air medical services was divided into two separate types to    |
| 004 | capture air medical flights under Part 135 and air medical     |
|     | flights not covered by Part 135                                |
|     |                                                                |
|     | A more clearly defined 'other' category was reintroduced       |
+-----+----------------------------------------------------------------+

The table below summarizes changes in survey implementation.

+-----+----------------------------------------------------------------+
| **  | **Description of change to survey implementation**             |
| Yea |                                                                |
| r** |                                                                |
+-----+----------------------------------------------------------------+
| 1   | Non-respondent telephone survey conducted to adjust active     |
| 999 | aircraft and hours flown estimates[^1]                         |
|     |                                                                |
|     | Sample design revised to stratify by aircraft type (19         |
|     | categories) and FAA region (9 categories)[^2]                  |
+-----+----------------------------------------------------------------+
| 2   | Discontinued non-respondent telephone survey because of the    |
| 000 | variability of telephone non-respondent factors                |
|     |                                                                |
|     | Added Internet response option                                 |
+-----+----------------------------------------------------------------+
| 2   | Added a reminder/thank-you postcard between the first and      |
| 003 | second mailings                                                |
+-----+----------------------------------------------------------------+
| 2   | Introduced "multiple aircraft" summary form to allow           |
| 004 | owners/operators of multiple aircraft to report aggregate data |
|     | for their entire fleet on a single form                        |
|     |                                                                |
|     | Sample design revised to stratify by aircraft type (19         |
|     | categories), FAA region (9 categories), and whether or not the |
|     | aircraft is owned by an entity certified to fly Part 135 (2    |
|     | categories)                                                    |
+-----+----------------------------------------------------------------+

The table below summarizes changes to the definition of the general
aviation population.

  ---------- ----------------------------------------------------------------
  **Year**   **Description of change to definition of the GA population**

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

  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 were eligible for
             selection into the survey sample

  2004       Aircraft reported as "registration pending" or sold (if sold
             status less than 5 years) on the Registry were retained in the
             definition of the survey population and were eligible for
             selection into the survey sample
  ---------- ----------------------------------------------------------------

The 2004 statistics in this report were derived from the twenty-sixth
GAATAA Survey, which was implemented in 2005.

**Improvements to the 2004 Survey**

As part of ongoing efforts to improve the survey data, three key changes
were made to the 2004 survey:

> 1\. Turbojets, turboprops, rotorcraft, Part 135, and Alaska-based
> aircraft were sampled at 100%.
>
> 2\. A parallel data collection track was developed specifically for
> operators of large numbers of aircraft. Although similar to protocol
> used in the past, each data collection track is discussed separately
> below under "Survey Method."
>
> 3\. The sample design was changed significantly by adding a third
> dimension to stratify based on Part 135 status.
>
> 4\. The survey population was expanded to include aircraft that are
> listed as sold or "registration pending" on the Registry.

Each of these improvement is discussed in further detail in subsequent
sections of this Appendix.

**Survey Population and Survey Sample**

The survey population for the 2004 General Aviation and Air Taxi
Activity and Avionics Survey includes all civil aircraft registered with
the FAA that are based in the U.S. or U.S. territories and that were in
existence and potentially active between January 1 and December 31,
2004.[^3] This [includes]{.underline} 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) and commuter operations not covered
    by Part 121.

-   Part 137: Agricultural aircraft operations.

Aircraft operating under Part 121 as defined in Part 119 are
[excluded]{.underline} 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 also excluded from the population---i.e.,
aircraft displayed in museums, aircraft destroyed prior to January 1,
2004.

The Aircraft Registration Master File, maintained by the FAA's Mike
Monroney Aeronautical Center in Oklahoma City, 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 2004 survey population, we used the Registry's
list of aircraft as of December 31, 2004.

The Registry, like all sample frames, is an imperfect representation of
the survey population. While it may exclude a very 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, several steps are taken to remove ineligible aircraft from
the sample frame. Specifically, this includes removing the following:

-   Aircraft missing key identifiers that are necessary for
    classification or merging with other data sources (e.g., N-number,
    serial number, make/model information)

-   Aircraft whose registration has been cancelled or revoked

-   Aircraft based in Europe or registered to a foreign company that
    have not returned flight hour reports

-   Aircraft that operate under Part 121

-   Aircraft destroyed or moved to museums prior to January 1, 2004

-   Aircraft reported sold before 1999 (5 years prior to survey
    year)[^4]

-   Aircraft that are flagged Postmaster Return (known to have incorrect
    address information) since before 1994 (10 years prior to survey
    year)

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-   Aircraft that are missing information on the registrant's name
    (i.e., the field is blank) (Aircraft for which the registrant is
    listed as "Pending" are retained in the survey population[^5])

-   Aircraft that lack information necessary to execute the sample
    design (i.e., aircraft type, FAA region)

The Registry included 355,970 aircraft as of December 31, 2004. After
excluding the aircraft described above, the sample frame contained
297,627 records used to define the general aviation population.

[Sample Design]{.underline}

The 2004 GAATAA Survey Sample is stratified by aircraft type (19), FAA
region in which the aircraft is registered (9), and whether the aircraft
operates under a Part 135 certificate (2). Part 135 aircraft were
identified using the FAA's Operations Specifications Subsystem (OPSS)
database that was merged with the Registry by N-number. The three
stratifying variables yield a matrix of 342 cells.

The 2004 survey sample included several types of aircraft that were
sampled at a rate of 1.0 (i.e., 100 percent sample). Because of the
FAA's interest in gaining a better understanding of the operation of
these aircraft, all such aircraft listed in the Registry were included
in the survey sample to ensure a sufficient number of survey completes
to support analysis and provide more precise estimates of fleet size and
aircraft activity. These include

-   100 percent sample of turbine aircraft (turboprops and tubojets)

-   100 percent sample of rotorcraft

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

-   100 percent sample of aircraft based in Alaska

Altogether, these aircraft contributed 42,657 observations to the 2004
survey sample.

Other aircraft that are not part of a 100 percent sample are subject to
selection based on sampling fractions defined for each cell in the
sample design matrix. Average annual flight hours is the primary measure
needed by the FAA to address survey goals. 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 identify the optimal sample size for each strata.
Aircraft are randomly selected from each cell in the matrix, subject to
the desired sample size. Strata that yield a very small sample size are
examined and adjusted to include all observations in the strata if
necessary. In 2004, an additional 33,002 aircraft were sampled at a rate
of less than 1.0, yielding a total survey sample of 75,659. Table A.1
shows the number of aircraft selected into the survey sample, by
aircraft type, as well as the proportion of the population represented
by the sample.

TABLE A.1: SURVEY SAMPLE AND POPULATION FIGURES BY AIRCRAFT TYPE

  ------------------------------- ----------------- ---------- --------------
  **Aircraft Type**               **Population**    **Sample   **Sample as
                                                    Size**     Percent of
                                                               Population**

  **Fixed Wing - Piston**                                      

  1 engine, 1-3 seats             65,180            12,566     19.3

  1 engine, 4+ seats              127,366           16,521     13.0

  2 engines, 1-6 seats            16,389            3,333      20.3

  2 engines, 7+ seats             7,065             2,335      33.1

  Piston: Other                   250               250        100.0

  **Fixed Wing - Turboprop**                                   

  1 engine                        2,678             2,678      100.0

  2 engines, 1-12 seats           5,497             5,497      100.0

  2 engines, 13+ seats            1,042             1,042      100.0

  Turboprop: Other                88                88         100.0

  **Fixed Wing - Turbojet**                                    

  2 engines                       9,465             9,465      100.0

  Turbojet: Other                 1,060             1,060      100.0

  **Rotorcraft**                                               

  Piston                          4,328             4,328      100.0

  Turbine: 1 engine               5,804             5,804      100.0

  Turbine: Multi-engine           1,299             1,299      100.0

  **Other Aircraft**                                           

  Glider                          3,212             1,372      42.7

  Lighter-than-air                7,295             1,780      24.4

  Experimental                                                 

  Amateur                         34,107            3,793      11.1

  Exhibition                      3,171             813        25.6

  Experimental: Other             2,331             1,635      70.1

  **Total**                       297,627           75,659     25.4
  ------------------------------- ----------------- ---------- --------------

[Weighting the Survey Data]{.underline}

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 a small adjustment for aircraft that are not part of the survey
population.

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 N~ijk~/Sample N~ijk~) \* (N Respondents~ijk~/Sample
N~ijk~)

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

The weight is subsequently adjusted to reflect new information about
non-general aviation aircraft. That is, survey responses that identify
an aircraft as not being part of the survey population---destroyed prior
to January 1, 2004; displayed in a museum; operated primarily as an air
carrier under Part 121 or 129; or a military aircraft---are used to
remove aircraft proportionally from the sample and from the population.
This adjustment is done at the level of the 19 aircraft types. The
procedure assumes that non-GA aircraft occur in the same proportion
among survey respondents and non-respondents. To the extent that non-GA
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]{.underline}

Errors associated with survey data can be classified into two
types---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 can be further subdivided into 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]{.underline}

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]{.underline}. 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.2 shows selected interval
widths and their corresponding confidence.

> TABLE A.2: CONFIDENCE OF INTERVAL ESTIMATES

  ----------------------------------- -----------------------------------
  [WIDTH OF INTERVAL]{.underline}     APPROXIMATE CONFIDENCE\
                                      THAT INTERVAL INCLUDES\
                                      [TRUE POPULATION VALUE]{.underline}

  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 simply 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) \* 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 provide an
example of how to compute and interpret confidence intervals. To obtain,
for example, a 95 percent confidence interval for the estimated number
of total hours flown for turbojets in 2004, where the total hours flown
is estimated to be 3,718,456 and the percent standard error of the
estimate is 1.2, the following computation applies:

> Lower confidence limit: 3,718,456 -- 2(1.2/100)(3,718,456) = 3,629,213
>
> Upper confidence limit: 3,718,456 + 2(1.2/100)(3,718,456) = 3,807,699

In other words, if we drew repeated samples of the same design, 95
percent of the estimates of the total hours flown by turbojets would
fall between 3,629,213 and 3,807,699.

[Non-sampling Error]{.underline}

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 fall into two
classes---strategies to reduce non-response and efforts to minimize
measurement and coding errors. To this end, implementation and design of
the 2004 GAATAA Survey incorporated the following steps to maximize
cooperation among sample members:

-   Two modes of administration to facilitate access to the survey---a
    postcard invitation to complete the survey on the Internet followed
    by a mail survey to be completed by pen or pencil

-   Three mailings of the survey to individuals who had not yet
    responded, as well as a reminder/thank-you postcard

-   Cover letters accompanying each survey mailing clearly explained the
    purpose of the survey as well as the endorsement (organizational
    logos) of several aviation associations[^6]

-   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
    survey."

-   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, updates from aviation associations)

-   Use of a toll-free 800 telephone number and email address to respond
    to questions

-   Collaboration with aviation organizations and industry groups to
    encourage cooperation of owners or operators of multiple aircraft

The survey also reflects efforts to minimize measurement error by
increasing the likelihood that respondents share a common understanding
of survey questions and reducing errors in data coding. These include:

-   Close collaboration with the FAA, other federal agencies and
    aviation groups to refine and clarify question wording as well as
    definitions to questions. The questionnaire is re-examined each year
    to identify ambiguities or revisions necessary to remain consistent
    with aviation regulations and definitions.

-   Significant reviews and re-designs of the questionnaire have been
    undertaken periodically (see "Background" section of this report).
    Each re-design is thoroughly pre-tested with a sample of aircraft
    owners or operators and, if necessary, modified on the basis of the
    pre-test results.

-   Comprehensive editing and verification procedures to ensure the
    accuracy of data transcription to machine-readable form as well as
    internal consistency of responses.

**Survey Content**

The 2004 GAATAA Survey questionnaire, shown in figure B.1 of Appendix B,
requests the aircraft owner or operator to provide the following
information on the sampled aircraft's characteristics and uses:

> 1\. Number of total hours flown in 2004, and hours flown by use
>
> 2\. Airframe hour reading and the aircraft's base location as of
> December 31, 2004
>
> 3\. IFR hours, percentage of hours flown in Instrument Meteorological
> Conditions (IMC) and Visual Meteorological Conditions (VMC) during the
> day and evening
>
> 4\. Number of landings in 2004
>
> 5\. Fuel type
>
> 6\. Whether the aircraft was part of a fractional ownership program in
> 2004
>
> 7\. Avionics equipage

**Survey Method**

Appendix B presents the materials used to conduct the 2004 survey. The
standard survey form is shown in Figure B.1. The postcard invitation to
the Internet component and the reminder/thank-you postcard are shown in
Figure B.2. Each of the three mailings for the standard survey was
accompanied by a cover letter, shown respectively in Figures B.3, B.4,
and B.5.

The protocol used for the 2004 survey is similar to that used since the
2000 survey. The survey data were collected from owners and operators of
the sampled aircraft through two venues -- the Internet and mailings of
the questionnaire. The Internet component was implemented before the
mailing portion to capture as many respondents electronically as
possible. Sampled aircraft were first sent a postcard inviting them to
participate in the Internet version of the survey. The postcard was sent
out on July 1, 2005, and the Internet component continued through
November 7, 2005.

There were three mailings of the standard questionnaire, and a
reminder/thank-you postcard sent between the first and second mailings.
The first questionnaire mailing, sent out on August 2, 2005, covered
49,819 aircraft in the sample that had not completed a survey via the
Internet or had not received a final disposition due to a returned
postcard (refused, respondent deceased, undeliverable with no new
address, etc.). The reminder/thank-you postcard was sent on August 12,
2005, and included only those aircraft in the sample that had not yet
responded to the survey and were not part of the non-active sample. The
second survey mailing was sent on September 2, 2005, and included only
those aircraft in the sample that had not yet responded to the survey
and were not part of the non-active sample. The third mailing was sent
on October 7, 2005, to owners and operators of the sampled aircraft who
had not responded to the first or second mailings.

[Alternative Survey for Reporting on Multiple Aircraft]{.underline}

The 2004 GAATAA Survey focused on increasing cooperation among
respondents who own or operate multiple aircraft. To achieve this
objective, the 2004 survey employed new data collection tools and
methods.

The responses of multiple-aircraft owners/operators are extremely
important for accurately estimating general aviation activity. Because
of the increased burden of reporting for multiple aircraft, there was a
concern that these high-end, high-use operators were less likely to
respond to the survey. Therefore, after the sample was selected, the
FAA's Operations Specifications Subsystem (OPSS) was used to group
aircraft belonging to the same operator's fleet. Operators with three or
more aircraft were classified as "multiple owners/operators" for survey
purposes, regardless of the number of their aircraft present in the
survey sample.

To avoid confusion among respondents, aircraft were assigned to a single
data collection track. The 10,411 aircraft in the "multiple
owner/operator" track followed an independent protocol new to the 2004
survey year. The remaining 65,248 aircraft followed the same protocol
used in previous years and is described above.

In order to minimize the reporting burden on operators of multiple
aircraft, a new summary survey was developed with the cooperation of
several aircraft operators and aviation associations to enable an
operator to report activity for an entire fleet on a single condensed
form, instead of completing the longer questionnaire for each individual
aircraft. This survey form (Appendix B, Figure B.6) allowed operators to
report on key variables for major classes of aircraft, including hours
flown, how flown, and number of landings. The form did not collect data
on flying conditions, fuel type, fractional ownership, or avionics.

Data collection for multiple-aircraft owners/operators began
approximately one month after the standard data collection track as the
methodology and materials were finalized. Once active, subsequent
mailings for multiple-aircraft owner/operators followed the same timing
as the standard protocol. Like the standard survey protocol, an Internet
survey that matched the mail questionnaire was programmed to allow
online reporting.

To maximize the survey response rate, follow-up phone calls were placed
to all multiple-aircraft owners/operators. These calls focused not only
on encouraging survey participation, but also on ensuring survey
mailings were reaching the appropriate person in the operators'
organization. In many cases, aviation associations with which operators
had an existing relationship made these telephone calls.

Benefits resulting from the new systems of data collection implemented
since 2000 include quicker processing of the results, improved data
quality, and considerable savings of time and money to both the public
and the federal government.

**Response Rate**

As shown in Table A.3, the overall response rate for the 2004 survey was
42.7% [^7]. The response rate for the Internet portion of the survey was
17.8 percent and accounted for 41.9 percent of the total responses to
the survey. The first mailing had a response rate of 14.9 percent and
accounted for 30.5 percent of the total responses to the survey. The
second mailing had a response rate of 10.5 percent, which accounted for
20.5 percent of the total responses to the survey. The third mailing
produced a response rate of 4.9 percent, approximately 7.1 percent of
the total responses to the survey.

TABLE A.3: SUMMARY OF RESPONSE INFORMATION

  ---------------- -------------- --------------- ------------- -------------
  **Phase**        **Valid        **Responses**   **Response    **% Total
                   Sample**[^8]                   Rate**        Response**

  Internet         75,301         13,441          17.8%         41.9%

  1^st^ Mailing    65,819         9,778           14.9%         30.5%

  2^nd^ Mailing    62,619         6,565           10.5%         20.5%

  3^rd^ Mailing    46,334         2,272           4.9%          7.1%

  Total            75,061         32,056          42.7%         100.0%
  ---------------- -------------- --------------- ------------- -------------

Table A.4 illustrates the steady increase in the Internet response as a
percentage of all returned surveys from 2000 to 2004 (16.4 percent for
2000 compared with 41.9 percent for 2004). This increase in response
suggests an increasing effectiveness of utilizing the Internet for data
collection, thereby improving the efficiency of the data collection
process.

TABLE A.4: PERCENTAGE OF ALL COMPLETED SURVEYS RESPONDING BY INTERNET

  ---------------- ---------- ---------- ---------- ---------- ----------
                   **2000**   **2001**   **2002**   **2003**   **2004**

  Total Completes  15,689     16,432     15,254     14,471     32,056

  Internet         5,144      5,954      5,304      6,059      13,441
  Completes                                                    

  Internet % of    32.8%      36.2%      34.8%      41.9%      41.9%
  Total                                                        
  ---------------- ---------- ---------- ---------- ---------- ----------

Table A.5 shows responses by aircraft type.

TABLE A.5: RESPONSE RATE BY AIRCRAFT TYPE

  ---------------------- ------------ -------------- --------------- ------------
  **Aircraft Type**      **Sample**   **Invalid      **Responses**   **Response
                                      Sample**[^9]                   Rate**

  **Fixed Wing -                                                     
  Piston**                                                           

  1 engine, 1-3 seats    12,566       105            5,847           46.9%

  1 engine, 4+ seats     16,521       75             8,008           48.7%

  2 engines, 1-6 seats   3,333        18             1,490           44.9%

  2 engines, 7+ seats    2,335        16             923             39.8%

  Piston: Other          250          6              65              26.6%

  **Fixed Wing -                                                     
  Turboprop**                                                        

  1 engine               2,678        18             1,170           44.0%

  2 engines, 1-12 seats  5,497        22             2,131           38.9%

  2 engines, 13+ seats   1,042        9              363             35.1%

  Turboprop: Other       88           2              17              19.8%

  **Fixed Wing -                                                     
  Turbojet**                                                         

  2 engines              9,465        57             3,755           39.9%

  Turbojet: Other        1,060        26             265             25.6%

  **Rotorcraft**                                                     

  Piston                 4,328        54             1,351           31.6%

  Turbine: 1 engine      5,804        38             1,858           32.2%

  Turbine: Multi-engine  1,299        11             571             44.3%
  ---------------------- ------------ -------------- --------------- ------------

TABLE A.5: RESPONSE RATE BY AIRCRAFT TYPE (CONT.)

  ---------------------- ------------ --------------- --------------- ------------
  **Aircraft Type**      **Sample**   **Invalid       **Responses**   **Response
                                      Sample**[^10]                   Rate**

  **Other Aircraft**                                                  

  Glider                 1,372        9               681             50.0%

  Lighter-than-air       1,780        34              646             37.0%

  Experimental                                                        

  Amateur                3,793        59              1,891           50.6%

  Exhibition             813          25              382             48.5%

  Experimental: Other    1,635        14              642             39.6%

  **Total**              75,659       598             32,056          42.7%
  ---------------------- ------------ --------------- --------------- ------------

[^1]: Telephone surveys of non-respondents also were conducted in 1977,
    1978, 1979, 1997, and 1998. Please refer to the 1999 GAATAA Survey
    report for a full discussion of the telephone survey of
    non-respondents.

[^2]: Before 1999, the sample was stratified by aircraft type (19
    categories) and state/territory (54 categories).

[^3]: According to the FAA Aircraft Registration Master File---the
    sample frame for the survey (discussed below)\--over 99 percent of
    the aircraft in the 2004 survey population were registered to owners
    in the 50 states, the District of Columbia, Puerto Rico or other
    U.S. territories, such as American Samoa, Guam, and the Virgin
    Islands.

[^4]: Prior to 2004, aircraft were excluded if reported sold more than 1
    year prior to the survey year.

[^5]: Prior to 2004, aircraft with "Registration Pending" were excluded
    from the population.

[^6]: The following associations' logos appeared on the 2004 cover
    letter: Aircraft Owners and Pilots Association (AOPA), Experimental
    Aircraft Association (EAA), General Aviation Manufacturers
    Association (GAMA), Helicopter Association International (HAI),
    National Agricultural Aviation Association (NAAA), National Air
    Transportation Association (NATA), National Business Aviation
    Association (NBAA), Small Aircraft Manufacturers Association (SAMA).

[^7]: Although the 2004 response rate of 42.7% represents a decrease
    from response rates prior to 2003, this decrease is attributable to
    changes in survey methodology that have occurred over the past 5
    years. The inclusion of bad addresses in the response rate
    calculation, adding more aircraft registered as "Sale Reported" or
    "Registration Pending" to the survey population, and other factors
    have resulted in the decrease to the response rate.

[^8]: Even though efforts are made to remove non-GA aircraft from the
    population before the sample is selected, a small number of surveys
    are returned each year indicating that the aircraft should not be
    part of the survey population (e.g., the aircraft was used primarily
    as a Part 121 air carrier, or was a museum piece the entire survey
    year). The Total Valid Sample Size used to compute the overall
    survey response rate excludes such aircraft.

[^9]: Even though efforts are made to remove non-GA aircraft from the
    population before the sample is selected, a small number of surveys
    are returned each year indicating that the aircraft should not be
    part of the survey population (e.g., the aircraft was used primarily
    as a Part 121 air carrier, or was a museum piece the entire survey
    year). The Invalid Sample represents such aircraft, which are
    excluded from response rate calculations.

[^10]: Even though efforts are made to remove non-GA aircraft from the
    population before the sample is selected, a small number of surveys
    are returned each year indicating that the aircraft should not be
    part of the survey population (e.g., the aircraft was used primarily
    as a Part 121 air carrier, or was a museum piece the entire survey
    year). The Invalid Sample represents such aircraft, which are
    excluded from response rate calculations.