Q&A
I'm too fatigued for my assigned duty but could do a shorter one. What do the rules say?
The CARs are silent on partial fitness — but AC 700-047 says it would be reasonable for the operator to reassign you to a duty you are fit for. What the CARs do require is that you tell the operator you're not fit for the assigned duty.
Turns on: CARs 700.26(1) , CARs 700.26(2)
What the CARs require
CARs 700.26(1): “An air operator shall not allow a flight crew member to begin a flight duty period if, before the beginning of the period, the member advises the air operator that they are fatigued to the extent that they are not fit for duty.”
And 700.26(2): if you become unfit during an FDP, you must tell every other flight crew member and the operator as soon as you’re aware of it.
Fit for duty is defined in CARs 101.01 — your ability to act as a flight crew member is not impaired by fatigue, alcohol or drugs, or any mental or physical condition. Only the flight crew member can decide whether they are fatigued to that extent (AC 700-047 § 4.2).
The gap: unfit for this duty, fit for a shorter one
The regulation speaks in absolutes — fit or not fit — and says nothing about a crew member who couldn’t safely do the assigned long day but could do a short local flight.
AC 700-047 § 4.11(3) fills that gap with guidance, not a rule:
If a flight crew member were to advise the air operator that they are unfit for the assigned duty but they are fit for a different duty, it would be reasonable for the air operator to reassign the flight crew member to the duty they are fit for.
So: tell the operator you’re not fit for the assigned duty (that part is required). Whether you’re then reassigned to something shorter is a reasonable operator decision the AC supports — it isn’t a right the CARs spell out.
See also: Maximum hours of work (700.29)