Cessna 120

The airframe is aluminium: sheet metal over a riveted frame, the way most aircraft have been built since the 1940s. Fabric-covered wings on most 120s. The FAA has issued 29 airworthiness directives (orders that owners must comply with) that name this model, most of them about flight controls. Operators and repair shops have filed 108 failure reports with the FAA since 1996, 97 of them in the last ten years: about 2.9 a year for every 100 aircraft on the register; the system most often named is airframe structure. 90 approved modifications exist for it, the most by Lowe Aviation Aircraft Maintenance.

Sources: the FAA's type certificate data sheets, airworthiness directives, supplemental type certificates, special conditions and special airworthiness information bulletins (Dynamic Regulatory System), and the FAA's service difficulty reports. A failure report is what an operator or repair station chose to file; the counts show reporting as much as reliability, and larger and commercial fleets report more. How the systems are grouped.