An inflight “fume event” so bad that two cabin crew were rendered unconscious may have had a more serious underlying cause than initially thought, according to a BBC investigation.
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, and discharged the same day.
At the time, the carrier said: “American Airlines flight 729 from London Heathrow to Philadelphia diverted to Dublin due to an odour caused by a spilled cleaning solution in the galley.”
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.
The airline has refuted the BBC assertions. An American Airlines spokesperson said “We take cabin odour issues seriously and have devoted extensive efforts over time, including working with aircraft, engine and auxiliary power unit manufacturers, to address these types of concerns.
"The odour that was detected by our crew on 21 October was not related to the APU, as the APU – including bleed air from the APU – was not operational during this time period and did not operate during this flight."
The aircraft was cleared to resume operations the day after the incident, after an American Airlines maintenance team was unable to replicate the odour
The spokesperson added: "After boarding in Dublin on 22 October, some of our crew members believed they detected the odour once again.
"The determination was made by our operations centre to rebook customers on alternate flights, and ferry the aircraft back to Philadelphia on 23 October with our three pilots.
"During that ferry flight back to Philadelphia, no odours were reported on the ground or in the air by our pilots."
"The health and welfare of our crews and customers continues to be our top priority. However, in the case of this aircraft and the diversion to Dublin, there is no connection to the APU or bleed air from the APU.”
At the Philadelphia base, the APU was replaced, and the aircraft began passenger flights on 25 October.
The Civil Aviation Authority says in a briefing to NHS medical staff: “Fume events – abnormal odours, smoke, haze or fumes in the cabin – may arise from various internal or external sources, and some are due to contamination of the bleed air supply, for example as a result of a failure of an oil seal in the engine.
“There is strong evidence that some people experience acute symptoms as a consequence of fume events.
“Some of the chemical contaminants that are present during such events are irritant, and may cause itching or soreness of the eyes, nasal discharge, sore throat or coughing.”