EasyJet plans to fit filters to stop toxic fumes entering passenger cabins and cockpits.

The move is being interpreted as the aviation industry’s first acknowledgment of “aerotoxic syndrome”.

The condition is feared to be responsible for several deaths of pilots and crew and hundreds of incidents where pilots have fallen ill, sometimes at the controls.

Frequent flyers and young children could also be affected, it is claimed.

EasyJet told The Sunday Times that “health concerns” had led it to work with a commercial supplier, Pall Aerospace, to “develop and design a new cabin air filtration system” for testing on the carrier’s aircraft next year.

Alex Flynn, head of campaigns at the Unite union, which represents cabin crew, said the easyJet move was “highly significant and welcome”.

He said Unite was involved in about 100 UK civil court actions for death and injury allegedly caused by cabin air.

A “handful” of cases had already been settled by airlines, although without any admission of liability.

During high-altitude flight the atmosphere is too thin to breathe so compressed air, or “bleed air”, is drawn from aircraft engines and directed into the passenger cabin and cockpit. It is cooled but not filtered.

Faults in engine seals can contaminate it with engine oil, hydraulic fluids and lubricants. Some air is then re-circulated through a filter, but a typical aircraft cabin consists of half re-circulated filtered air and half unfiltered bleed air.

The new “total filtration” system being tested by easyJet will for the first time filter the bleed air as well. It also includes a contamination detector.

EasyJet insisted it was not taking a position on aerotoxic syndrome, which “remains an area of scientific uncertainty”.

David Stein, Pall’s vice-president for aerospace research and development, is due to describe the trial at a conference in London this week held by the Global Cabin Air Quality Executive.