During a dispute within friends, it came to my attention that in 135.65 the maintenance log copies must be present in the aircraft, and that 91.407(b) and 91.417(c) have similar rules, but, meanwhile, as indicated in 91.203 the "maintenance logs" are not necessarily maintained and be present in the aircraft. Why is this?

Why didn't a school provide the maintenance logs in the aircraft, but only the airworthiness certificate?

I don't understand the reason behind this; if it must be present in the aircraft for 135 operations (air taxi) why it is not present in 91 operations? Safety wise speaking, I think any pilot who commands a plane, abused by many different people, would want to know what was in the maintenance logs?

I tried to understand the reasoning: maybe the regulators think that it will create another responsibility for PIC? Or maybe this added responsibility will diminish the part 91 owner/operator responsibility? If anybody can explain the underlying rationale for the legislation ıt will be great.

  • $\begingroup$ Welcome to aviation.SE! It looks like you have two questions: why are the part 135 and part 91 regulations different? And should pilots expect to see maintenance logs from a school or FBO? Your second question might be answered here; does it help at all? $\endgroup$
    – Pondlife
    Commented Jan 24, 2021 at 19:26
  • 3
    $\begingroup$ Part 91 includes Farmer Joe who takes his J-3 around the pattern at his grass strip more often than he takes it out of sight of the farm. Keeping his maintenance log in the hanger makes more sense than stowing it (where?) in the plane. Part 91 rules can be pretty "minimalist" that way, while -135 and -121 are much (much!) more structured. $\endgroup$
    – Ralph J
    Commented Jan 24, 2021 at 20:10
  • $\begingroup$ In Canada you don't keep any maint documentation in the plane, but every a/c has to have a Journey Log where flights are recorded. You just record date, to/from, air time, flight time, total hours, and make short notations of maintenance competed. This is separate from the tech logs. When you purchase an a/c in Canada you have its complete flight history, where it's been, etc. When you own a homebuilt, as I do, you can actually record all of the maintenance in the Journey Log and aren't legally required to keep tech logs. I keep copies of Journey Log flight and maint entries at home. $\endgroup$
    – John K
    Commented Jan 25, 2021 at 3:33

2 Answers 2


For the same reason truckers are required to keep logs in their trucks noting rest times, inspections, etc. but private vehicle owners do not. Part 135 is for commercial operations, part 91 is not.


Part 135 maintenance log refers to aircraft maintenance discrepancy log, which is a book with

  • current aircraft times,
  • travel log with destination codes and Hobbs hours,
  • airframe landing count and engine cycle count, and
  • space for a pilot to write a discrepancy, so the mx facility can review and work on the issue and sign it off right in the mx log.

It is a legally bound document needed for part 135 operator because they carry passengers. It is not a whole suitcase with aircraft records (which are actually stored in a facility in fireproof archive cabinets).

You don't need a maintenance log for part 91 privately owned aircraft, unless you want to track all your legs and time, like a flight school does.


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