A 100-hour inspection is the FAA-mandated inspection required every 100 flight hours for aircraft used commercially for hire or flight instruction. The limit may be exceeded by up to 10 hours only to reach a maintenance facility, with the overrun deducted from the next interval.
The 100-hour inspection is the FAA-mandated inspection required every 100 hours of time in service for aircraft used to carry persons for hire or for flight instruction for hire (14 CFR 91.409(b)). Its scope is essentially identical to the annual inspection; the difference is authorisation — an A&P mechanic may sign off a 100-hour, while an annual requires Inspection Authorization (IA).
The rule contains one carefully bounded flexibility: the 100-hour limit may be exceeded by up to 10 hours, but only to fly the aircraft to a place where the inspection can be performed — and the overrun is deducted from the next 100-hour interval, so the next inspection comes due early. It is a positioning allowance, not a buffer.
Why it matters for flight schools
For US flight schools the 100-hour is the metronome of fleet planning: a busy trainer hits it monthly, and each event costs one to several days of availability. Schools that forecast due dates against booking load schedule inspections into naturally quiet windows; schools that don't discover them when the tach catches up — usually mid-week with a full schedule. Misunderstanding the 10-hour allowance (treating it as routine slack) is a classic violation pattern the FAA looks for.
How FlightLogger handles it
FL Maintenance projects each aircraft's 100-hour due point from live tach data against the booking calendar — so inspections land in planned slots instead of ambushing a full training week.
Frequently asked questions
Does hour building or rental require a 100-hour inspection?
The requirement applies to aircraft carrying persons for hire and aircraft provided by a person who also provides the flight instructor. Pure rental without instruction is a nuanced area — many operators apply 100-hour inspections across the fleet regardless, both for safety and simplicity.
Can the 100-hour interval legally be exceeded?
Only by up to 10 hours, and only to reach a place where the inspection can be done. The excess is subtracted from the next interval, and using the allowance for ordinary revenue flying is a violation.