A British Airways plane from London to New York made a U-turn over the Atlantic and diverted to Shannon Airport in Ireland after the crew reported smoke on board.
Flight 173 was over two hours into its journey when it turned around, reports RTE News.
Emergency services had been standing by but returned to the fire station just before the jet landed safely at 6.20pm on Thursday.
The pilot had contacted air traffic control to say the smoke had dissipated and the matter was under control.
A replacement aircraft was flown in from Heathrow and passengers continued their journey at 1am on Friday morning.
It is the second time in less than a week that a British Airways Boeing 777 made an unscheduled stop at Shannon because of smoke on board.
Last Saturday, the crew of British Airways Flight 177, also travelling from Heathrow to New York's JFK Airport, had to don oxygen masks and broadcast a May Day distress call after they detected smoke in the cockpit, reports the Clare Herald.
The paper added that the May Day call was accidentally broadcast over the jet's PA system so passengers heard the transmission.
Plane makes emergency landing in Dublin after 'smoke in cockpit'
Thomas Cook holiday plane makes emergency landing after 'fire in cabin'