India on Thursday put all of its major airports on high alert following warnings of possible attacks using hijacked airlines, officials said. The alert was sounded after Defence Minister A.K. Antony ordered the armed forces to be on guard against "any terror strikes from the air," officials said. "This is based on a warning which has been received by the government and we are prepared as usual," Air Chief Marshal Fali Major told reporters. Government sources said all major airports -- including New Delhi, Bangalore, Mumbai and Kolkata were on high alert.