According to reports, the directive has come following intelligence inputs in the wake of the terror attack at the Pathankot air base.
Security has been beefed up at Indira Gandhi International Airport and both domestic and international flights have been asked to upgrade the scale of security, with some passengers being made to undergo secondary ladder checking in some flights.
A secondary ladder checking is conducted just when the passenger is about to enter the aircraft with an aim to ensure that he is not carrying any weapon or chemical.
Staff of several airlines has been sensitized about the alert, asking them to report any suspicious movement or object.
The Central Industrial Security Force, which guards the high-valued installation, has been asked to maintain extra vigil with the deployment of additional personnel.
Earlier, Delhi Police Commissioner B S Bassi had said that the city police is prepared to foil any kind of bid from terror elements.
He said Delhi Police always remains in touch with central intelligence agencies and State governments to gather information in this regard.
He added that necessary steps have been taken to meet any kind of eventuality.
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