New Delhi, Oct. 5 -- A British Airways flight travelling from London to Chicago suddenly declared an emergency over Ireland on Monday after making a sudden and steep descent, with flight-tracking data showing the aircraft dropping by around 28,000 ft.

British Airways Flight BA295 was operating from London Heathrow to Chicago O'Hare when then incident occurred. The Boeing 777-200ER, registered as G-VIIA, had departed Heathrow Terminal 5 at around 11.50 AM local time and was scheduled to operate an approximately eight-hour-40-minute transatlantic journey.

Flight-tracking data showed the aircraft dropping to approximately 9,000 feet while flying over Ireland. Shortly after the descent began, the crew reportedly transmitted 7700, the intern...