Airline roster norms explained: How duty hours and rest rules impact flights?

After IndiGo cancelled 150 flights on Wednesday and 250 on Thursday, throwing major airports across India into chaos, the discussion began on how the carriers operate daily. The airline that operates around 2,200-2,300 flights daily to over 90 domestic and 45 international destinations said in a statement that it had initiated "calibrated adjustments" to its schedules for the next 48 hours. With this, focus shifted to the airline roster norms. What are the airline roster norms that have thrown airlines' operations out of gear many times in the past as well?

Airline Roster Norms

In a nutshell, the airline roster norms are the rules that govern how the pilots and cabin crew members are scheduled to work. These include duty hours, time off, rest periods, a cap on the night flights and a lim