As the plane prepared to take off around 7:50 a.m. Tuesday, a Cray member on flight 6E 6543 noticed a male passenger standing at the back of the plane.

"There was an error in the passenger boarding process from Mumbai to Varanasi in which a standby passenger was allotted a seat reserved for a confirmed passenger," the airline said in a statement.

“The error was noticed before departure, and the standby passenger was offloaded. This caused some delay. IndiGo will take all measures to strengthen its operational processes. The statement said it regrets the inconvenience caused to customers.