How the data is built

• Service difficulty reports (SDRs): the FAA’s Service Difficulty Reporting System, every yearly file from 1995 to the current year. An SDR is a write-up of a failure, malfunction or defect filed by an operator, repair station or mechanic.
• Fleet size: the FAA aircraft registry (releasable database), counting aircraft with a valid or pending registration, on the date shown on each page.
• Airworthiness directives: FAA final rules under 14 CFR Part 39 published in the Federal Register. Federal Register coverage is thin before 1998, so older ADs may be missing.
• Accidents: the NTSB’s aviation accident database (1982–2007 and 2008–present files). Pages count U.S. accidents since 1995, excluding homebuilt aircraft.

Accidents are matched to an aircraft family by the make and model the NTSB recorded. Phase of flight is the phase of the event the NTSB marked as defining the accident; for older records it is the first recorded occurrence. Cause findings use the NTSB’s own wording and categories and are available from 2008 on. NTSB files some pilot-control findings (for example, directional control not maintained) under “Aircraft”; Squawkbook shows those as “Aircraft performance and control” to keep them apart from mechanical findings about aircraft systems and powerplant.

Accident counts are not rates. They depend on fleet size, hours flown and how the aircraft is used (for example, flight training), so they should not be compared across aircraft types.

A language model reads each AD’s applicability section and lists the aircraft, engine, propeller and component models it names. An AD is shown on an aircraft page when it names one of that family’s models, or an engine model family used in its registered fleet. ADs replaced by a later AD are left off. The plain-English summaries are machine-written from the AD text; the AD itself is the authority, and every entry links to it.

Applicability depends on serial numbers, engine models and installed equipment, and ADs for components (magnetos, instruments, seat belts and so on) are only shown when they list the aircraft. Always check the FAA’s official AD records for a specific airplane.

SDRs record the aircraft make and model as free text in FAA abbreviations. Each distinct make/model string is matched to a model in the FAA registry’s aircraft reference table: first by exact rules, then by suggestions from a language model that a person reviews. Only matches at high confidence are counted. Models are then grouped into families by hand, and each page says which variants its family includes.

Systems are the FAA’s Joint Aircraft System/Component (JASC) codes as entered by the person filing the report. Codes are sometimes missing or inconsistent, so treat system shares as approximate.

• Reporting is voluntary for most private operators (Part 91). Flight schools, repair stations and charter operators report far more, so counts reflect who reports as much as what breaks.
• Counts are not a reliability or safety ranking, and should not be compared across aircraft types.
• The per-1,000 figure divides recent reports by today’s registered fleet. It is a rough scale, not a failure rate.
• Reports appear only after FAA quality review, so the current year is incomplete.

Squawkbook does not display aircraft registration (N) numbers or aircraft serial numbers. They are removed from report text before publication, and results are shown only at the model level.

The site uses Google Analytics to count visits and see which pages are read. Pre-buy card marks stay in your browser and are never sent to us.

If a report is assigned to the wrong aircraft or a figure looks wrong, a corrections form is coming with the public launch. Mechanics’ and inspectors’ corrections are especially welcome.

This site is informational. Always follow the aircraft’s maintenance manual, applicable airworthiness directives and your mechanic’s judgment.