A British Airways flight bound for Chicago declared an emergency after rapidly descending around 28,000 feet over Ireland on Monday, before turning back towards London and spending hours at low altitude ahead of its return to Heathrow.

Flight BA295, operated by a Boeing 777-200ER, was travelling from London Heathrow to Chicago O’Hare when it descended from around 37,000 feet to approximately 9,000 feet while crossing Ireland.

The aircraft transmitted the emergency transponder code 7700 before abandoning its transatlantic journey. 

Flight-tracking data showed the aircraft remained airborne for several hours after the emergency began, flying at about 9,000 feet and circling over southern England and the English Channel rather than immediately landing.

A tracker showed the flight had been live for nearly four hours by around 8:48pm Bangladesh time, with the aircraft still at 9,000 feet. It was travelling at a ground speed of about 249 knots at the time.

The prolonged low-altitude flying appeared consistent with the aircraft needing to reduce its landing weight before returning to Heathrow. Aviation reports said the aircraft had lowered its landing gear while circling to increase drag and accelerate fuel burn. 

Flight data subsequently listed Heathrow as the diverted destination, with an estimated arrival of around 5:08pm local time. The aircraft, registered G-VIIA, had left Heathrow at 11:50am. 

British Airways had not immediately disclosed what prompted the emergency.

The steep descent to 9,000 feet could be consistent with procedures used during a pressurisation problem, but there was no official confirmation that cabin pressure was the cause.

The 7700 transponder code signals a general emergency to air traffic controllers but does not identify its nature. It can be used for a range of situations, including technical or medical emergencies.

Monday’s incident came just days after another dramatic aviation emergency involving flydubai Flight FZ1073, which was travelling from Dubai to Tel Aviv on September 30.

The flydubai Boeing 737 descended more than 16,000 feet in roughly 35 seconds during an onboard crisis, according to flight data analysed by CNN. Its speed increased sharply during the descent, approaching the speed of sound, CNN reported. 

Authorities said the flydubai co-pilot attacked the captain and allegedly attempted to take control of the aircraft. Passengers and off-duty pilots intervened, and the plane eventually made an emergency landing in Tabuk, Saudi Arabia. 

Flight-tracking data showed FZ1073 first transmitted the general emergency code 7700 before briefly switching to 7500 — the internationally recognised code for unlawful interference with an aircraft — and later returning to 7700 before landing safely. 

The 7700 code is an internationally recognised transponder signal used by pilots to alert air traffic control to a general emergency.

It does not identify the nature of the problem. A flight may squawk 7700 because of a technical malfunction, medical emergency or another situation requiring priority handling from air traffic controllers. 

Flight-tracking data subsequently showed BA295 diverting back to London Heathrow, abandoning its planned transatlantic journey to Chicago. 

There were no immediate reports of injuries, and details about the number of passengers and crew aboard were not available.

The incident remains developing, with British Airways yet to disclose the cause of the emergency.

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