Air India on Monday asked its passengers to arrive at airports three hours before the departure time of their flights. Security has been tightened across airports after terror threat alert was issued following the Pathankot attack, in which seven security personnel and six militants were killed.

"In view of the recent security alert in the country, passengers/baggage may have to undergo more stringent checks at airports... To avoid any delays to the flight departures owing to these procedures, AI has requested passengers to report at the counter well in time for check-in," The Times of India cited Air India advisory issued on Monday.

The advisory will remain in place till the Republic Day celebrations.

According to the Directorate General of Civil Aviation's rule, domestic passengers have to report 75 minutes before the scheduled departure time of flights, while international passengers have to report 150 minutes in advance.

The airlines have been advised to thoroughly screen all passengers and their baggages, an Air India official said.

"Screening has been enhanced... Earlier some cabin bags were randomly opened for checking at security frisking counters. Now, either all bags or anything even remotely suspicious is being thoroughly scrutinised," TOI quoted the airline official as saying.

He added that the enhanced security checks will take more time so people are advised to reach the airports earlier "to avoid missing flights and also ensure flights leave on time despite enhanced security".

Mumbai's Chhatrapati Shivaji International Airport (CSIA) is already following the instructions; the baggages are being checked in case of suspicion, "vehicles coming near the airport are also being checked more diligently in view of the terror threat", Daily News & Analysis quoted a CISF officer at CSIA as saying.