A number of former and serving cabin crew are reported to be planning legal action against British airlines saying they have been poisoned by contaminated cabin air.
The cases are funded by the Unite union which represents 20,000 flight staff.
The cabin crew believe they have fallen sick after breathing in fumes mixed with engine oil and other toxic chemicals.
The Civil Aviation Authority says incidents of smoke or fumes on planes are rare and there is no evidence of long-term health effects.
The Unite union, which is calling for a public inquiry into contaminated cabin air, recently opened a dedicated legal unit to record and process claims from its membership.
Its lawyers are working on 17 “definite” individual personal injury claims against UK airlines in the civil courts, although these are still at an early stage.
Uncensored safety reports submitted to the CAA, and obtained by the BBC’s Victoria Derbyshire programme, show that between April 2014 and May 2015 there were 251 separate incidents of fumes or smoke inside a large passenger jet operated by a British airline.
An illness was reported in 104 of the 251 cases, and on at least 28 of those flights oxygen was administered.
The programme also said it had seen a first-hand testimony from a pilot working for a major UK airline who believes he was affected by toxic fumes while landing at Birmingham airport in 2014.
Airbus and Boeing both maintain cabin air is safe to breathe.