New Delhi: A pilot of IndiGo - an airline known for being largely on time - was caught blaming the Air Traffic Control for a delay in take-off, even though it was caused by the absence of his co-pilot.

The take-off of the Chennai-Madurai flight 6E-859 last week was delayed by 40 minutes - which was conveyed to the passengers by text message. But the pilot later announced that the flight had been further delayed "because the Air Traffic Controller was not clearing the aircraft for departure," a source said.

What gave him away was the presence of a member of the Air Traffic Control on board. "The controller called up the Chennai ATC to know the reason for the delay in clearance," another source said. But he was told that no such thing has happened.

The ATC member went to meet the pilot in the cockpit and found the co-pilot was not in his seat.

The Airports Authority of India raised the issue with IndiGo and the pilot was given a warning by the ATC. The commander later apologised "unconditionally" for the delay and announced that it was due to the absence of his co-pilot.

The IndiGo Airlines sent an e-mail to its pilots, asking them not to indulge in such action, said sources. In a detailed response, the airline, however, said the flight was delayed by three minutes.

"Our captain while monitoring ground frequency noticed there was ramp and air congestion prevailing on other aircraft and proactively made an announcement citing the same," a spokesperson of the airline said. "The ATC personnel travelling as a passenger came up and spoke to the captain and our captain made a second announcement".

The airline, however, pointed out that "we would have appreciated had the said passenger taken up the issue through proper channel instead of intervening with the operating crew before a flight, when they need to focus on procedures and safety."