Examples of instructors rosters
Typical instructor roster:
sim sessions from midnight till 0400 am, for 2 or 3 days, 1 day off then AMM, ISB, DXB, DEL, 2 days off, LHR, one night layover, JED,1 day off SIM, SIM, SIM, SIM, CAI, BOM
Typical line captain roster form the same period:
SIN 4 days, 2 days off, PEK 3days, 3 days off, BEY, FRA one night, 2 days STBY,1 day off, MLE 2 days layover, 3 days off.
You can change the name of the destination to match your fleet but the concept remains valid.
Instructors are not only required to remain alert to teach, but also avoid and correct the trainees mistakes even when tired by such duty cycle.