An Air India source told NDTV that the pilots did leave the cockpit for 20 minutes.
More than 150 passengers were on board.
In a statement today, Air India conceded that the flight attendants "were in the cockpit for a prolonged period" and "due to distraction, the co-pilot had touched the auto pilot disconnect button momentarily." However, it said, "at no point of time the cockpit was left unattended by the cockpit crew." (Read: Air India's full statement)
Newspaper reports today said that while the pilots were sleeping, one of the stewardesses accidentally undid the auto-pilot setting, and that the pilots then raced back to take charge.