After initially claiming spilt soap led to a flight being diverted and resulted in two unconscious crew members, American Airlines has backtracked after the aircraft's maintenance records show otherwise.

The incident

On October 21, American Airlines flight AA729 was diverted after leaving London Heathrow for Philadelphia. The plane was forced to land in Dublin after a strong odor was detected in the cabin. The fumes were so strong than upon landing in Dublin, two crew members and one passenger required immediate medical attention and were taken to hospital.

The airline initially brushed the incidence off as the result of “dish soap in a bottle” according to an internal report on the incident.

In an audio clip published by The Telegraph, the captain of the Airbus A330-300 can be heard stating that a cleaning product from London Heathrow was accidentally left in an aircraft toilet and had spilled. The captain seems to believe that it is this substance which caused two crew members to lose consciousness.

The airline claims the aircraft was inspected after the incident by a team of “highly skilled” engineers. Whatever the result of this investigation, the plane continued to be operational and just two days later, on October 23, a similar situation occurred on the same plane when an odor caused "eye and throat irritation".

New evidence

Despite the airline's statement, the BBC is claiming they have “other evidence” which tells a different story. Reportedly, the plane suffered an oil leak before the flight which the BBC claims could have caused “toxic fumes to enter the cabin.”

Although American Airlines continues to deny this, they have now changed their initial story stating that soap “was not the source of the odor”.  So if soap isn’t responsible, could the oil leak have caused the odor?

The oil leak

According to the aircraft’s maintenance log, the leak occurred in the Auxiliary Power Unit (APU) which provides power to the engines and runs the onboard electrics when the main engines are not running. Three days before the flight to London, a report showed that the APU had "high oil consumption", 31.75 pints in just two weeks, and says the APU was "wet with oil".

On its own, this wouldn’t amount to much evidence, but according to the BBC, another report states that the APU was inoperable and needed to be repaired in the next few days.

American Airlines claims the issues with the APU were not responsible as the unit was “not operational during this time period and did not operate during this flight". However, Airbus, the manufacturer of the aircraft, gives the opposing view that even if the APU was not operational during the flight, it could still be responsible.

An Airbus article entitled "A clean APU means clean cabin air" clearly states that the situation could arise when the APU is not running. This is because the oil which leaked may have entered the aircraft's air-conditioning system.

The airline has continued to deny this, stating that "in the case of this aircraft and the diversion to Dublin, there is no connection to the APU or bleed air from the APU."

So what did cause the smell?

Well, at this stage, it isn’t exactly clear. American Airlines has said that "It cannot be emphasized enough that the health and welfare of our crews and customers continue to be our top priority.” However, it has not yet given a reason for the odor.

Despite not knowing what caused the incident which left two unconscious, the aircraft is still operational and has flown a further 39 flights.

What do you think caused the odor in this circumstance? Was the soap responsible, was it the APU oil leak or could it be something else entirely? Let us know in the comments below.