100-Hour Inspection for Flight School Aircraft: Who Needs It

A trainer at 99.8 hours can't legally finish a 1.5-hour dual lesson, but the same airplane at 95 hours can go out on a 10-hour weekend rental. Those two answers, from an FAA Chief Counsel letter, sum up when a flight school aircraft needs a 100-hour inspection. It needs one when the school provides it and the instruction is for hire. Under 14 CFR 91.409(b), nobody may give flight instruction for hire in an aircraft they provide, or carry anyone other than crew for hire, unless the aircraft has had an annual or 100-hour inspection within the preceding 100 hours of time in service. For a flight school that covers nearly every trainer on the line, leaseback airplanes included. Pure rental, to pilots who fly the airplane themselves, is where most of the confusion comes from.

1. What 91.409(b) says about flight school aircraft

The rule, from eCFR: "no person may operate an aircraft carrying any person (other than a crewmember) for hire, and no person may give flight instruction for hire in an aircraft which that person provides, unless within the preceding 100 hours of time in service the aircraft has received an annual or 100-hour inspection." It continues: "The 100-hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done. The excess time used to reach a place where the inspection can be done must be included in computing the next 100 hours of time in service."

So there are two triggers, carrying a non-crew person for hire and paid instruction in an aircraft the instructor or school provides. The 10-hour allowance is narrow. It covers flying to the shop, and the hours it uses come off the next interval. Aircraft on an approved progressive inspection program under 91.409(d) follow that program instead.

Part 141 doesn't change anything. The FAA has pointed out that 14 CFR 141.39(a)(3) requires each aircraft a Part 141 school uses for flight training and solo flights to be maintained and inspected under the rules for aircraft operated for hire.

2. Does a rental aircraft need a 100-hour inspection?

Not when the school only rents it. The best FAA source on this is a pair of letters to Fly By Knight, a Part 61 and 141 school in Hammond, Louisiana. The Office of the Chief Counsel answered in October 2014, then reissued the answer in October 2015 with a corrected response to the last question; the 2015 letter replaces the 2014 one. Its core point is that the requirement "depends on how the aircraft is operated during the flight in question." The school asked about specific cases, and the answers belong on the dispatch desk:

• Aircraft at 95 hours, renter takes it for a 10-hour weekend trip, school provides no pilot. Not a violation. The rule doesn't apply to that flight.
• Aircraft at 99.8 hours, 1.5-hour local dual lesson. A violation once the 0.2 hours run out. The 10-hour allowance doesn't cover local training.
• Aircraft at 99.8 hours, 2.5-hour solo cross-country by a student. Also a violation. Solo training flights are instruction.
• Aircraft at 97 hours, a 3.0-hour dual cross-country planned, which runs 3.1 because of vectors and wind. Not a violation, because nobody intended to overfly.
• Aircraft at 100 hours, marked rental only for three days while it waits for the shop. Renters can keep flying it, but it can't go back to instruction until it's inspected.

A later letter, answering a 2017 request from Blue Line Aviation in Raleigh, closed the obvious loophole. The rule applies when the school provides the aircraft and the instructor, receives compensation, and flight training is given. A school "cannot avoid the 100-hour inspection requirement by not charging separately or explicitly for the instructor," for example by folding the instructor into the rental rate or membership fees. It applies even if the instructor is the school's owner rather than an employee. A renter checkout with no flight training in it isn't instruction and doesn't trigger the rule.

3. The edge cases

The student brings their own airplane

The rule turns on who provides the aircraft. If the student owns it and the school supplies only the instructor, the school isn't giving instruction in an aircraft it provides, so on the plain wording the 100-hour doesn't attach to that airplane. The annual still does. None of the letters cited here addresses this case directly, so confirm it with your FSDO or an aviation attorney before you build a pricing model on it.

The independent CFI

Same logic. A freelance CFI teaching in the owner's airplane isn't providing the aircraft. A CFI who owns a 152 and sells lessons in it is, and that 152 is on the 100-hour clock.

The flying club

A club that rents its airplanes to members who fly themselves sits in the rental-only bucket. A club that provides the airplane and a paid club instructor for lessons, or for checkouts with training in them, starts to look like the Blue Line case, and that letter says folding the cost into membership fees doesn't change the answer. If your club offers in-house instruction, ask an aviation attorney whether the training airplanes belong on 100-hour inspections. Our post on flying club checkout requirements covers what those checkouts should include.

4. 100-hour vs annual: which counts for which?

An annual satisfies the 100-hour, because 91.409(b) asks for "an annual or 100-hour inspection" in the preceding 100 hours. The reverse isn't automatic. Under 91.409(a), a 100-hour inspection counts as the annual only if it's done by a person authorized to perform annuals (an IA) and entered in the records as an annual. If you want the two clocks to reset together, ask for that.

An annual doesn't buy back overflown hours either. The Fly By Knight letter took the case of an aircraft that flew 105 hours, the last 5 en route to the shop. The next inspection is due in 95 hours whether the shop signs it off as an annual or a 100-hour.

5. Worked example: tracking the 100-hour on a leaseback

Say you own a 172 on leaseback to a school that flies it about 40 hours a month, nearly all of it lessons. The last 100-hour was signed off at 4,210.0 (use whichever meter your maintenance records are kept on), and the annual was signed in March 2026.

1. The next 100-hour is due at 4,310.0. At 40 hours a month, that comes around roughly every ten weeks.
2. Tuesday night the meter reads 4,304.6, so 5.4 hours are left. Wednesday has two 1.5-hour local lessons and a 3.0-hour dual cross-country on the schedule.
3. The two lessons fly and leave the airplane at 4,307.6. The cross-country would plan to overfly by 0.6, which the FAA's letter calls a violation. It moves to another tail or waits for the inspection.
4. Thursday the airplane flies 0.4 to the shop at the next field and arrives at 4,308.0. The 100-hour is signed off there, so the next one is due at 4,408.0. You gave up 2 hours of interval, which is cheaper than a violation.
5. Variant: the nearest open shop slot is 2.9 hours away and the airplane arrives at 4,310.5. That's legal under the 10-hour en-route allowance, but the next 100-hour is due at 4,410.0, not 4,410.5.
6. The annual signed in March 2026 is due by the end of March 2027 however many 100-hours happen in between, unless one of them is done by an IA and entered as the annual.

Two things belong in the leaseback agreement. First, who decides whether the airplane flies rental only while it's out of hours and waiting for a shop slot. The 2015 letter says that's legal, but it's your engine. Second, who pays for each inspection and the squawks it turns up. At roughly five inspections a year at that pace, those invoices are a large part of whether the leaseback makes money.