AD burden by model which business jets and turboprops carry the most FAA airworthiness directives

METHODOLOGY

How the ADs are counted

• Source. Every final rule under 14 CFR part 39 in the Federal Register, 1995 to October 1, 2026: 12,857 directives for every kind of product. The Federal Register’s online edition starts in 1994 with a handful of ADs, so earlier ADs, some still in effect on older types, are not counted.
• Matching. An AD counts for a type when its title or applicability names the type certificate holder (or a predecessor) and the FAA model designator the type is registered under. A match means the AD may apply: serial numbers, installed equipment and modifications decide whether it applies to one aircraft. For a designator that starts with a number (the Citation 650, 700 or 680A, the Learjet 45 or 60), the number counts only in a model list (“Model 650”, “Models 525, 525A, and 525B”, “Cessna 650 series”) under the same maker, never as a serial number, part number or address. ADs that list their models only in a table image, and spellings the matcher does not read, can leave a few ADs unmatched.
• Airframe ADs only. Only ADs issued for airplanes are counted. Engine, propeller and appliance ADs that do not name the aircraft are excluded, and so are those that list it among the aircraft they can be installed on, so the model AD pages, which also list those, can show more.
• In effect. Not superseded by a later AD and not removed, as far as the Federal Register shows. Recurring: the AD’s text requires repetitive actions.
• Grouping. Model pages registered under the same FAA designators share every AD and are shown as one row; the Learjet 35A and 36, one type certificate whose ADs name the models apart, are combined. Airliners and piston aircraft are left out.

Radar reads an aircraft’s logbooks and ties each AD to the entries that show how it was complied with. See AD tracking in Radar.