Weather 
A British Airways flight started descending 27,000 feet about 30 minutes after it departed London on Monday en route to Chicago, according to flight data.
A spokesperson for British Airways said there was a technical issue and that the aircraft later landed safely.
The jet had dropped to 9,000 feet from 36,000 feet over a period of several minutes, tracking data from FlightAware shows. It appeared to be a controlled descent.
The plane turned around over Ireland and circled for a few hours, data shows, apparently to burn off fuel. It later landed back at Heathrow Airport Monday evening local time.
“Customers disembarked the aircraft normally and our teams are working to get their travel plans back on track as quickly as possible,” the airline spokesperson said.
Amanda Forssell and Sarah Ploss contributed to this report.
