India, Oct. 5 -- A transatlantic British Airways flight operating from London to Chicago on Monday rapidly descended 28,000 feet after about an hour into its journey, tracking data on flightradar24 showed.

The flight BA295 declared an emergency after squawking 7700 and descended from an altitude of 37,000 feet to an altitude of 9,000 feet within minutes. The flight then made a U-turn back to the United Kingdom, and landed at London's Heathrow airport, from where it had departed earlier.

The flight, which took off from London's Heathrow Airport at around 11.50 am local time, according to flight tracking data, and had a scheduled flight time of eight hours and 40 minutes to Chicago O'Hare International Airport (ORD).

After takeoff, it st...