Aviation watchdog DGCA has ordered that if a flight does not initiate takeoff within five minutes of air traffic control (ATC) clearance, it will be moved to the end of the queue and allowed to depart only when a slot is available.
It will help prevent a ripple effect on operations if a flight gets delayed.
"Approval for push back and start up shall be valid for five minutes only. Aircraft not adhering to push back clearance will go back in the sequence. Subsequent clearance will be given based on available slot," read an order issued by the DGCA on September 27.
The instructions have been issued to all scheduled airlines and airport operators and are meant for "strict compliance".
"Aircraft shall complete all pre-departure checks and cabin procedures prior to entering the runway and start rolling as soon take-off clearance is issued by the ATC," it said.
Airlines not adhering to their time slots will lose their "historicity" during the preparation of schedule for the next season, which means a poor track record will spoil their chances of getting the sought after slots such as those available during peak hours.
The regulatory body has also asked the airports to ensure that departure slots are "distributed evenly within an hour with not more than five departure slots in 10 minutes and total of 30 per hour".
They will also have to ensure that no two aircraft with departure within 20 minutes are parked on the same block of parking bays.
The airports in Delhi and Mumbai are facing severe constraints and have not been able to accommodate new flights during peak hours due to unavailability of slots.