How long must aircraft maintenance records be kept?

There is no single answer, and the short answers in circulation are often wrong. Under both FAA and EASA rules, records of individual pieces of work can be discarded after a set period, while the records that establish an aircraft's current status, including the life of its life-limited parts, stay with the aircraft for as long as it flies.

FAA: two kinds of record, two retention rules

14 CFR 91.417 divides maintenance records in two.¹ Paragraph (a)(1) covers records of maintenance, preventive maintenance, alteration and inspection: what was done, when, and the signature and certificate number of the person approving return to service. Those "shall be retained until the work is repeated or superseded by other work or for 1 year after the work is performed."

Paragraph (a)(2) covers status: total time in service of the airframe, engines, propellers and rotors; the current status of life-limited parts; time since last overhaul; current inspection status; airworthiness directive status; and copies of Form 337 for major alterations. These have no expiry. They "shall be retained and transferred with the aircraft at the time the aircraft is sold," and 91.419 requires the seller to hand them over.²

The common claim that "the FAA requires records for one year" describes only the first category. The records that matter most over an aircraft's life are the ones with no end date.

Air carriers (Parts 121 and 135)

The structure is the same, with one addition: records of the last complete overhaul are kept "until the work is superseded by work of equivalent scope and detail," and status records again transfer with the aircraft on sale.^3,4

Repair stations (Part 145)

A certificated repair station "must retain the records required by this section for at least 2 years from the date the article was approved for return to service."⁵ That is the repair station's own copy; the owner's obligations under Part 91, 121 or 135 run separately.

EASA: what the aircraft keeps, and what organisations keep

Under Part-M, point M.A.305 sets the aircraft's continuing-airworthiness record system.⁸ The technical log must cover "the 36 months period prior to the last entry." Detailed maintenance records and airworthiness directive records are kept until superseded by equivalent information, covering a period of no less than 36 months. An in-service history record for each life-limited part is required, with no end date while the aircraft is in service.

When an aircraft is permanently withdrawn from service, M.A.305 requires the core life data to be "retained for at least 12 months." A widely repeated figure of "36 months after withdrawal" is not what the rule says. On transfer of the aircraft, M.A.307 moves the records with it and the same retention periods continue to apply to the new owner or operator. Part-ML (ML.A.305) sets similar rules for lighter general aviation aircraft.

Organisations

• Part-145 maintenance organisations keep detailed maintenance records, certificates of release to service and associated data "for 3 years from the date when the aircraft or component to which the work relates" was released (145.A.55).
• CAMOs keep records until 3 years after responsibility for the aircraft has been permanently transferred (CAMO.A.220).
• CAOs keep maintenance records for 3 years from release to service, and continuing-airworthiness management records for 2 years after the aircraft is permanently withdrawn (CAO.A.090).

Side by side

Life-limited parts and "back to birth"

Both regimes require the current life status of life-limited parts. Under 14 CFR 43.10, anyone removing such a part must keep its status known, by a record system that "may include electronic, paper, or other means of record keeping," and must "transfer with the part the mark, tag, or other record" when it is sold.⁶

A full history to the part's manufacture, often called back-to-birth, is what lessors and buyers ask for. The FAA's Chief Counsel has said the regulations themselves do not require it: "the regulations do not require 'back to birth' records in order to determine the life status of life-limited parts."⁷ In practice the market does, because a part without a provable history is worth far less.

Why this is a long-term integrity problem

The records with the longest lives are the status and life-limited-part records, and they are increasingly kept and signed electronically. A record kept for the life of an airframe will be read and relied on decades after it was signed. Whether its signature still proves anything by then is a separate question, covered in electronic signatures on maintenance records and post-quantum signatures for records that must last 30 years.