Airlines generally overbook to limit the possibility of a flight departing with vacant seats.

The incident took place at around 7.50 am on Tuesday just before the flight was scheduled to takeoff, reports said. The crew member noticed a male passenger standing at the rear end of the aircraft when flight 6E 6543 was taxiing, reports said.

“It was then that the crew alerted the pilot and the flight had to return to the terminal,” a Hindustan Times report quoted Sandeep Pandey, one of the passengers, as saying.

Another passenger Akhilesh Chaubey, who was going to Varanasi on a work trip, said, “The flight returned to the bay and the passenger was offloaded. The airline then checked the cabin baggage of all passengers on board before proceeding with the take-off after a delay of at least an hour,” he said.

According to flight tracking website Flightradar24, the aircraft took off at 8.41am.

“There was an error during the passenger boarding process of 6E 6543 from Mumbai to Varanasi, wherein a standby passenger was allotted a seat reserved for a confirmed passenger. The error was noticed prior to the departure of the aircraft, and the standby passenger was de-boarded. This led to a slight delay in the departure of the aircraft," the report quoted an airline spokesperson as saying.

"IndiGo will take all measures to strengthen its operational processes and regrets the inconvenience caused to customers,” the spokesperson said.