Cabin crew can only work for a specific number of hours in a week/month/year. In Europe, flight time for an attendant cannot exceed 1,000 hours in a year. On the other hand, a flight attendant cannot have a flight time greater than 900 hours in the UK. ICAO defines fatigue as, A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload, and as a result, pilots, too, have restrictions on the maximum number of hours they can fly.