Cause of British Airways emergency landing at YVR still a mystery as plane returns to service

The British Airways aircraft that made an emergency landing in Vancouver last week has returned to service even though authorities were never able to find the exact cause of the problem.

Initial reports suggested smoke in the cabin but that was never the case, according to Bill Yearwood of the Transportation Safety Board.

"British Airways and Airbus have exhausted their techniques to find any clues or cause of the reported and apparent odour [but] there is no definitive answer," he said.

The aircraft has since been returned to active service. Yearwood said the file has been closed and the Transportation Safety Board will not be investigating any further.

But in a press release Unite a British trade union that represents cabin crew says the incident is an example of the airline downplaying crew exposure to fumes, which the union say is an industry-wide problem.

''Strong noxious smell' blamed

According to a Transport Canada incident report flight BA286 bound from San Francisco to London was diverted to Vancouver for an emergency landing after several cabin crew members and a passenger became ill due to a "strong noxious smell" on the upper flight deck.

The aircraft an Airbus A380, the largest passenger jet in the world was carrying 388 passengers and 25 crew.

All 25 crew and one passenger were hospitalized when the plane landed, and were later released with no apparent lasting illness.

The flight was initially diverted to Calgary but then diverted again to Vancouver where the airport is better equipped to handle an A380.

Maintenance crews checked the plane over on the ground in Vancouver but were unable to find the source of the problem.

The plane was then flown to Heathrow airport in London with only flight and maintenance crews aboard in an attempt to replicate the issue, but crews were still unable to find the source of the problem.

Fuel dumped to allow safe landing

The TSB report also revealed the plane dumped fuel in order to land safely at the Vancouver airport.

Yearwood says this is standard practice in a situation where an aircraft needs to make an emergency landing so soon after takeoff and can only be done in areas designated by Transport Canada.

This is done at cruising altitude generally over water and the fuel dissipates in the air long before reaching the ground, he said.

"It just atomizes in the atmosphere," he said.

The design of a long-range passenger aircraft like the A380 assumes that most of the fuel will have been burned by the time the plane lands and its maximum allowable landing weight is actually much lower than its maximum allowable takeoff weight.

If possible, Yearwood said pilots will usually just fly the plane in circles over their landing site until enough fuel has been burned to allow for a safe landing.

But in a more serious medical or mechanical emergency fuel can be jettisoned instead to allow for a quicker landing.