Every general aviation airplane needs an annual inspection. Some also need a 100-hour inspection. The two cover the same checklist, so owners often wonder why both exist. The difference is in when they're required and who can sign them off.
This guide covers the rules in 14 CFR §91.409 for typical piston airplanes. Aircraft on a progressive inspection program or another approved program follow different rules.
The annual inspection
Under §91.409(a), nobody may operate an aircraft unless, within the preceding 12 calendar months, it has had an annual inspection and been approved for return to service.
- Calendar months means the inspection is due at the end of the month, 12 months later. An annual signed off on March 3 is good through March 31 of the following year.
- It must be performed by a mechanic holding an Inspection Authorization (IA), a certificated repair station appropriately rated, or the aircraft's manufacturer. An A&P mechanic without an IA cannot sign off an annual.
- The scope follows Part 43 Appendix D: the whole airplane, inside and out.
If the annual expires, the airplane isn't airworthy. You'd need a special flight permit (a "ferry permit") to fly it somewhere for the inspection.
The 100-hour inspection
Under §91.409(b), a 100-hour inspection is required when an aircraft is:
- carrying any person (other than a crewmember) for hire, or
- provided by any person giving flight instruction for hire.
In practice that means rental airplanes, flight school airplanes and airplanes used for paid passenger rides. A privately owned airplane flown only by its owner does not need 100-hour inspections, even if the owner flies it more than 100 hours a year.
Key points:
- The scope is the same Part 43 Appendix D checklist as an annual.
- An A&P mechanic can sign off a 100-hour inspection. No IA is needed.
- It's due every 100 hours of time in service. Many operators track this on the tach (see Hobbs vs tach time).
The 10-hour overfly
The 100-hour limit may be exceeded by up to 10 hours while en route to a place where the inspection can be done. The excess comes off the next interval: if you do the inspection at 105 hours, the next one is due 95 hours later.
An annual counts as a 100-hour, but not the other way round
An annual inspection satisfies the 100-hour requirement. A 100-hour does not satisfy the annual requirement. Many flight schools time one of their 100-hour inspections to be done by an IA as the annual, resetting both clocks at once.
The flight-instruction question
The rule says "provided by any person giving flight instruction for hire". The common interpretation:
- If a flight school or instructor provides the airplane and charges for instruction, it needs 100-hour inspections.
- If you own the airplane and hire an instructor to teach you in it, the instructor isn't providing the airplane, so no 100-hour is needed.
Situations like leasebacks, flying clubs and LLC-owned airplanes can be less clear-cut. Ask your mechanic or your FSDO if you're unsure.
Side by side
| Annual | 100-hour | |
|---|---|---|
| Required for | Every aircraft (unless on another approved program) | Aircraft carrying people for hire, or provided for flight instruction for hire |
| Interval | 12 calendar months | 100 hours of time in service |
| Who can sign it off | IA, repair station, or manufacturer | A&P mechanic (or the above) |
| Scope | Part 43 Appendix D | Part 43 Appendix D |
| Can substitute for the other? | Yes, counts as a 100-hour | No |
| Overfly allowance | None (special flight permit needed) | Up to 10 hours to reach an inspection location |
What else is due at inspection time
The annual is a natural moment to catch up on other recurring items, though each has its own rule and interval:
- Airworthiness Directives with recurring compliance (see AD compliance).
- Transponder checks every 24 calendar months (§91.413).
- Pitot-static and altimeter checks every 24 calendar months for IFR flight (§91.411).
- ELT inspection every 12 calendar months, and battery replacement per its schedule (§91.207).
- Oil changes and other manufacturer-recommended maintenance.
Tracking these on one list, by date and by hours, is what keeps an airplane legal without surprises.
Frequently asked questions
Does a privately owned airplane need a 100-hour inspection?
Not if it's only flown by its owner and not used to carry people for hire or provided for flight instruction for hire. It still needs an annual inspection every 12 calendar months.
Can an A&P mechanic do an annual inspection?
An A&P can perform the work, but the annual must be signed off by a mechanic with an Inspection Authorization (IA), an appropriately rated repair station, or the manufacturer.
Can you fly past the 100-hour inspection?
Yes, by up to 10 hours, but only to reach a place where the inspection can be done. The extra time is deducted from the next 100-hour interval.
Does an annual inspection reset the 100-hour clock?
Yes. An annual inspection meets the 100-hour requirement, so the next 100-hour inspection is due 100 hours after the annual.