This bizarre footage shows the moment passengers on a flight were left alarmed - by a BAT soaring through the aircraft.

The stowaway passenger was spotted on board a 15-hour Air India flight from Delhi, India, to Newark, USA, on Thursday (May 27) - and prompted an emergency landing.

Passengers were left twisting in their seats to keep a wary eye on the Indian flying fox - as the large animal was left flying in agitated circles through the cabin of the Boeing 777 airplane.

The flight captain informed Air Traffic Control of the bizarre incident just half an hour into the long-haul flight, the plane was advised to turn around and make an emergency landing.

Just an hour and a half after taking off from Delhi at 2.20am, passengers found themselves once again grounded back in the Indian capital city when the plane landed at 3.55am.

When wildlife experts boarded the plane to retrieve the bat, it was found dead in the Business Class section.