On 21 October 2019 an American Airlines Airbus A330 departed from Heathrow at 11.14am, destination Philadelphia.
Flight #AA729 was about 80 minutes into the flight and 200 miles southwest of Ireland when it turned around and landed at Dublin.
The cause: fumes in the cabin, which caused a burning sensation in the eyes and throat, as well as itchy skin.
Some of those onboard were severely affected. Two members of cabin crew were rendered temporarily unconscious. They were taken to hospital, along with one passenger.
But the BBC claims to have seen documents that casts doubt on the stated cause. It says an internal American Airlines report says the cause was from a bottle of washing-up liquid, but quotes an insider from the company saying it was “inconceivable” that a substance approved for use on a plane could cause two people to pass out.
The BBC says: “Records show part of the aircraft had been leaking oil prior to the flight.”
It reports that an “overpowering” smell was detected on the planes’ previous flight, AA728 departing on 20 October, from Philadelphia to London.
The plane’s auxiliary power unit (APU), which provides power when the engines are off, was described as “wet with oil”.
The cabin air supply on modern aircraft is from “bleed air” – hot air from taken from the compressor stage of jet engines, as well as from the APU.