The warning was issued on Wednesday, Dec 3 by the Bureau of Civil Aviation after a mail, which said that on December 6, terror groups might strike at these airports, trying to hijack a plane.
Since the threat came, the three airports have become like fortresses. However, this could not prevent a firing scare from bringing Delhi's international airport to a halt for almost an hour a little after 1 am on Friday.
Passengers have been asked to report three hours in advance so that thorough security checks can be done.
All hand baggages are being physically checked by security forces even after they have been put through the X-ray.
Apart from it, all cars approaching the airports are being checked thoroughly.
CISF and NSG commandos have been deployed at all three airports. Anti-sabotage and quick reaction teams have also already been formed at these airports and all airlines have been informed.