Aircraft maintenance tracking means knowing, for every aircraft, what inspections and tasks are required, when each one comes due by date, hours or cycles, and whether it was done and signed off. Under Part 91 the owner or operator carries that responsibility (14 CFR 91.403(a)). The work splits into four parts: the inspection program the aircraft is on (91.409), the records you must keep and for how long (91.417), airworthiness directives (part 39), and life-limited parts. All of it runs on a few counters: total time in service, cycles and calendar dates.
Who is responsible for aircraft maintenance tracking?
The owner or operator. Section 91.403(a) says: “The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.”
Your mechanic, repair station or director of maintenance does the work and signs for it. Knowing what is due, and making sure it gets done before the aircraft flies past it, stays with the owner or operator. Under 91.405, the owner or operator must also “ensure that maintenance personnel make appropriate entries in the aircraft maintenance records.”
Which inspection program is your aircraft on?
The program sets the intervals you track. Section 91.409 offers several; the aircraft type and the kind of flying decide which apply.
| Program | Rule | Who it applies to | Interval |
|---|---|---|---|
| Annual inspection | 91.409(a) | Most aircraft not on another program | Within the preceding 12 calendar months |
| 100-hour inspection | 91.409(b) | Aircraft carrying anyone other than crew for hire, or used for flight instruction for hire in an aircraft the instructor provides | Within the preceding 100 hours of time in service |
| Progressive inspection | 91.409(d) | Owners or operators who request it from the Flight Standards office | Set in the inspection schedule; complete inspection within each 12 calendar months |
| Selected program under (e) and (f) | 91.409(e), (f) | Large airplanes (part 125 not applicable), turbojet multiengine airplanes, turbopropeller-powered multiengine airplanes, turbine-powered rotorcraft | Set by the program selected |
| Part 125 or 135 approved program | 91.409(c)(2) | Aircraft identified in a certificate holder’s operations specifications | Set by the approved program |
The annual inspection
Paragraph (a) says no person may operate an aircraft unless, “within the preceding 12 calendar months,” it has had “an annual inspection in accordance with part 43 of this chapter and has been approved for return to service by a person authorized by § 43.7 of this chapter.” Track it by date.
The 100-hour inspection
Paragraph (b) applies to an aircraft “carrying any person (other than a crewmember) for hire” and to flight instruction for hire in an aircraft the instructor provides. It needs “an annual or 100-hour inspection” within the preceding 100 hours of time in service. An annual counts for the 100-hour. Under paragraph (a), a 100-hour does not count as an annual unless “it is performed by a person authorized to perform annual inspections and is entered as an ‘annual’ inspection in the required maintenance records.”
The rule allows a 10-hour overflight and charges it to the next interval. “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.”
With illustrative numbers:
- The last 100-hour inspection was done at 2,340.0 hours airframe total time.
- The next one is due at 2,440.0.
- The aircraft is ferried to the shop and arrives at 2,446.0, inside the 10-hour allowance.
- The next inspection is still due at 2,540.0, counted from 2,440.0 and not from 2,446.0. The 6 hours over come out of the next interval.
For maintenance records, time in service “means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing” (14 CFR 1.1). That is airborne time, which is usually less than the block time on a trip sheet. Block time in the counter brings every hourly item due early.
Progressive inspection
A progressive program spreads the inspection over smaller visits. It starts with a written request to the responsible Flight Standards office and needs an inspection procedures manual with an inspection schedule. The program’s frequency and detail “shall provide for the complete inspection of the aircraft within each 12 calendar months” (91.409(d)).
If you stop the program, two things start counting. “The first annual inspection under § 91.409(a)(1) is due within 12 calendar months after the last complete inspection of the aircraft under the progressive inspection,” and the 100-hour “is due within 100 hours after that complete inspection.” Record which visit was the last complete inspection.
Large and turbine multiengine airplanes: 91.409(e) and (f)
Paragraph (e) covers large airplanes (to which part 125 does not apply), turbojet multiengine airplanes, turbopropeller-powered multiengine airplanes and turbine-powered rotorcraft. A large aircraft is one “of more than 12,500 pounds, maximum certificated takeoff weight” (14 CFR 1.1). These aircraft skip the annual and 100-hour. Instead they must comply with life-limited part replacement times and be inspected under a program selected under paragraph (f). Turbine-powered rotorcraft may use the annual, 100-hour or progressive options instead.
Paragraph (f) lists four programs to choose from:
- A continuous airworthiness inspection program in use by a part 121 or 135 certificate holder operating that make and model.
- An approved aircraft inspection program approved under § 135.419 and in use by a part 135 certificate holder.
- “A current inspection program recommended by the manufacturer.”
- A program the owner or operator writes and the FAA approves under paragraph (g).
The owner or operator “must select, identify in the aircraft maintenance records, and use” one of them, and must include in it “the name and address of the person responsible for scheduling the inspections required by the program.” Each task in such a program can carry its own interval in hours, cycles, calendar time or a mix, and each one needs its own row in your tracking.
If you change programs, paragraph (h) says “the time in service, calendar times, or cycles of operation accumulated under the previous program must be applied in determining inspection due times under the new program.” Carry your counters across.
Part 135 operators have their own maintenance rules on top of these. Aircraft with nine passenger seats or fewer are maintained under parts 91 and 43 plus named part 135 sections; ten or more, under a part 135 maintenance program (14 CFR 135.411). Our comparison of Part 91, Part 135 and Part 91K covers how the rule sets differ.
What maintenance records must an owner or operator keep?
Section 91.417(a) sets out two kinds of record, kept for different lengths of time.
The first kind is the record of each piece of work: “maintenance, preventive maintenance, and alteration and records of the 100-hour, annual, progressive, and other required or approved inspections,” for the aircraft and each engine, propeller, rotor and appliance. Each record must include:
- A description of the work performed, or a reference to data acceptable to the Administrator
- The date the work was completed
- “The signature, and certificate number of the person approving the aircraft for return to service”
The second kind is the aircraft’s running status. Paragraph (a)(2) requires records containing:
- “The total time in service of the airframe, each engine, each propeller, and each rotor.”
- “The current status of life-limited parts of each airframe, engine, propeller, rotor, and appliance.”
- “The time since last overhaul of all items installed on the aircraft which are required to be overhauled on a specified time basis.”
- “The current inspection status of the aircraft, including the time since the last inspection required by the inspection program under which the aircraft and its appliances are maintained.”
- “The current status of applicable airworthiness directives (AD) including, for each, the method of compliance, the AD number and revision date. If the AD involves recurring action, the time and date when the next action is required.”
- Copies of the Form 337 for each major alteration to the airframe and currently installed engines, rotors, propellers and appliances.
If you can produce those six things for each aircraft, current to the last flight, your tracking does its job.
How long do you keep aircraft maintenance records?
Section 91.417(b) sets three periods:
| Record | How long to keep it |
|---|---|
| Work records under (a)(1) | “Until the work is repeated or superseded by other work or for 1 year after the work is performed” |
| Status records under (a)(2) | “Retained and transferred with the aircraft at the time the aircraft is sold” |
| A list of defects given to you under § 43.11 | “Until the defects are repaired and the aircraft is approved for return to service” |
Keeping every work record costs little and helps when the aircraft is sold, but the rule’s minimum is the table above. The owner or operator must make all of these records available on request to the FAA or an authorized representative of the NTSB (91.417(c)).
Altimeter, static system and transponder checks under 91.411 and 91.413 are left out of 91.417(a), but they still come due “within the preceding 24 calendar months” for IFR flight in controlled airspace and for a required transponder. Put them on the list anyway. The same goes for your 30-day VOR check.
How do you track airworthiness directives?
An airworthiness directive is a legally enforceable rule that applies to “aircraft, aircraft engines, propellers, and appliances” (14 CFR 39.3).
Missing one is a violation: “Anyone who operates a product that does not meet the requirements of an applicable airworthiness directive is in violation of this section” (39.7).
ADs apply to engines, propellers and appliances as well as the airframe, so check each serial-numbered product on the aircraft, not only the type. For each AD that applies, 91.417(a)(2)(v) requires the AD number and revision date, the method of compliance, and for a recurring AD “the time and date when the next action is required.”
A recurring AD has an interval, a last-done point and a next-due point, like any inspection. Track it on the same list.
An alternative method of compliance can be proposed under 39.19, but “you may use the alternative you propose only if the manager approves it.” Keep the approval with the AD record.
What are life-limited parts, and how do you track them?
Some parts have a mandatory replacement time. Section 91.403(c) says no one may operate an aircraft whose maintenance manual or instructions for continued airworthiness contain an airworthiness limitations section “unless the mandatory replacement times, inspection intervals, and related procedures specified in that section” have been complied with, or approved alternatives. For the aircraft it covers, 91.409(e) adds the replacement times for life-limited parts in the aircraft specifications, type data sheets and other documents approved by the FAA.
Life limits are often in cycles rather than hours, and they belong to the part, not to the aircraft. When a part moves from one engine or aircraft to another, its time and cycles go with it. Track each life-limited part by serial number, with:
- Its limit (hours, cycles or calendar time, whichever the document sets)
- Time and cycles accumulated so far
- What is left, and the airframe or engine reading at which it runs out
Which counters do you need to track?
Most aircraft need some or all of these counters:
| Counter | Usually drives | Notes |
|---|---|---|
| Airframe total time in service | 100-hour inspection, hourly tasks, 91.417(a)(2)(i) | Airborne time per 14 CFR 1.1, not block time |
| Engine time, each engine | Engine inspections, time since overhaul | Differs from airframe time after an engine change |
| Cycles | Life-limited parts, pressurization and gear tasks | Count them the way the limit’s source document defines a cycle |
| Landings | Gear and brake tasks | For tasks counted in landings rather than cycles |
| APU hours | APU inspections and overhaul | Read from the APU meter |
| Calendar date | Annual, 24-month checks, calendar-limited tasks | No counter to read; the date is the counter |
| Propeller or rotor time | Propeller and rotor inspections, overhaul | Required in 91.417(a)(2)(i) |
Update the counters after every flight, from the flight log.
How to set up aircraft maintenance tracking
These steps work in a spreadsheet or in software.
- List every aircraft and component. Airframe, each engine, each propeller or rotor, the APU, and each appliance or part with its own limit, by serial number.
- Record each counter’s current reading. From the logbooks, with the date of the reading.
- Name the inspection program. Which 91.409 program the aircraft is on.
- Enter every maintenance item. Each inspection, task, recurring AD, life limit and calendar check gets one row with its interval in hours, cycles, months or a combination.
- Record when each was last done. Date and counter reading at completion, and who signed it off.
- Calculate the next due point. Last done plus interval, for each limit the item has. For an item with two limits (“12 months or 600 hours”), track both; the item is due at whichever comes first.
- Give each item a status. For example: current, coming due within a set margin, or overdue. Pick margins that give your shop enough lead time, such as 30 days or 30 hours (illustrative).
- Update after every flight and every sign-off. Each sign-off resets the item from its completion point, except where a rule says otherwise, like the 100-hour allowance above.
Here is an illustrative due list for one aircraft, taken on a day when the airframe reads 2,412.0 hours, 1,804 cycles and 1,290 landings:
| Item | Interval | Last done | Next due | Remaining | Status |
|---|---|---|---|---|---|
| Phase inspection 1 | 300 hours or 12 months | 2,140.0 h, March 2026 | 2,440.0 h or March 2027 | 28.0 h | Coming due |
| Recurring AD (example) | 500 cycles | 1,350 cycles | 1,850 cycles | 46 cycles | Coming due |
| Main gear brake assembly | 2,000 landings | 410 landings | 2,410 landings | 1,120 landings | Current |
| Altimeter and static check (91.411) | 24 calendar months | November 2024 | November 2026 | Weeks | Coming due |
| Life-limited disk (example) | 15,000 cycles | New at 0 | 15,000 cycles | 13,196 cycles | Current |
All rows are illustrative.
Turn remaining hours into dates. If this aircraft flies about 30 hours a month (illustrative), the phase inspection’s 28 hours will run out in under a month. Our guide to aircraft maintenance forecasting covers how to project due dates from recent use.
Common aircraft maintenance tracking mistakes
- Tracking only one limit on a dual-limit item. “12 months or 300 hours” is due at whichever comes first.
- ADs checked against the airframe only. Engines, propellers and appliances carry their own ADs (39.3).
- Life-limited parts tracked by aircraft. The time belongs to the serial number and moves with it.
- No program named in the records. Aircraft under 91.409(e) must have the selected program identified in the maintenance records (91.409(f)).
- Deferred items forgotten at the next inspection. Equipment left inoperative under 91.213(d)(2) must be repaired, replaced, removed or inspected at the next required inspection (91.405(c)). See our guide to inoperative equipment under 91.213.
Aircraft maintenance tracking in Avion Desk
Avion Desk gives each aircraft one profile with its files and history, and tracks hours, cycles and other counters, with a forecast from recent use that says when items come due. Maintenance items come due by date or counter, are signed off, and carry a status calculated for you. Defects are logged, deferred or used to ground the aircraft, and cleared with the signer’s certificate number kept encrypted. You can bring your fleet, maintenance items and counters in from CSV, so you don’t retype a spreadsheet you already keep. See the aircraft and maintenance features and pricing.
To try it, start a free trial, import your maintenance items from CSV and see what’s due, or request a demo.
Frequently asked questions
Who is responsible for tracking aircraft maintenance?
The owner or operator. 14 CFR 91.403(a) makes them “primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39,” the airworthiness directive rules (91.403).
How long must aircraft maintenance records be kept?
Records of individual work are kept until the work is repeated or superseded, or for one year after it is done. Status records (total time, life-limited parts, time since overhaul, inspection status, AD status and major alteration forms) are kept and transferred with the aircraft when it is sold (91.417(b)).
Does a Part 91 aircraft need a 100-hour inspection?
Only if it carries anyone other than a crewmember for hire, or is used for flight instruction for hire in an aircraft the instructor provides. Otherwise the annual inspection applies, unless the aircraft is on a progressive program or a program under 91.409(e) and (f) (91.409).
What must an AD record show?
For each applicable AD: its number and revision date, the method of compliance, and, if it recurs, the time and date when the next action is required (91.417(a)(2)(v)).
This article explains the rules in plain language and isn’t legal advice; the regulation text governs.
