Passengers on board a plane that was reportedly hijacked from Bombay to New Delhi say the pilot had announced the episode was a security drill.
Government officials, however, denied the episode was a planned exercise, insisting they believed it was a hijacking.
Chandrakant Kharge, a passenger and member of parliament from the ruling coalition, said the pilot announced that "it was an exercise".
That was after the airliner carrying 54 passengers and crew had been on a runway at Indira Gandhi International Airport for more than an hour.
"If this was an exercise, it should not have lasted more than an hour. This has put the whole nation in a state of anxiety and concern," said Mr Kharge.
Civil Aviation Minister Shahnawaz Hussain insisted that the episode was not a government-planned security drill.
He told reporters that an anonymous phone call claiming a hijacking was made to an air traffic control station in the western Indian city of Ahmadabad, setting off the chain of events.
Other passengers confirmed that the pilot, Captain Ashwini Behl, announced it had been an "exercise" and not to panic.
"It was a normal landing. But then the plane was taken to one side. Runway lights were switched off. At 2.30am, the pilot announced that a hijacking had taken place," said Arun Sathe, also a senior politician.
"But he asked us not to panic. Then eight or nine commandos boarded the plane and surrounded one man whom they addressed as 'Sharma'. Then we were asked to leave."