The parents of a former British Airways pilot have spoken to the Tonight programme for the first time about his death.
Judith and Peter Westgate believe their son, Richard, was poisoned by repeated exposure to contaminated cabin air.
In February, the coroner leading his inquest wrote to the regulator and the airline to highlight his concern that passengers and aircrews were being exposed to organophosphates.
Richard Westgate was on medical leave when he died in December 2012. He was 43-years-old. His parents watched his health decline.
"It was mostly bad headaches", Judith Westgate told Tonight. "He thought at one moment perhaps he had a brain tumor, but that was obviously ruled out by scans and things and then it was when his circulation and numbness developed he was really frightened I think.
"I would liken the situation as increasingly advanced stages of multiple sclerosis. In other words, the nerve connections in the body breaking down," explains Peter Westgate.
The Westgates believe Richard died because of "aerotoxic syndrome" a condition that the aviation industry doesn't recognise.
The family says it was an enormous relief when the coroner investigating Richard's death, Sheriff Stanhope Payne, was so concerned by the evidence he had seen that he wrote to the Civil Aviation Authority and British Airways to explain that in his opinion "there is a risk future deaths will occur unless action is taken". It's an opinion they contest.
Ever since the coroner's intervention the family's hopes have been raised. "Richard's real dying wish almost was for us to work to stop this condition afflicting anybody else, whether it was flying crew or passengers alike" explains Judith Westgate.
You may not realise but when we fly some of the air we breathe is drawn from the engine.
As a result potentially harmful chemicals can and do get inside the aircraft, like organophosphates which are added to jet oil to prevent engine parts from wearing out and over-heating.
"Fume events" as the industry calls them are extremely rare and when they happen the government and the regulator say there is no proof they are harmful.
In its submission to the coroner the CAA said "there is no positive evidence of a link between exposure to contaminants in cabin air and possible acute and long-term health effects" although it concedes "such a link cannot be excluded".
The expert opinion of the independent Committee on Toxicity is quoted by both the CAA and British Airways in their responses to the coroner.
Tonight spoke to the head of the committee, Professor Alan Boobis, who believes that in "normal" conditions cabin air is safe but he points out that no one has ever managed to capture what happens during a fume event and it is therefore not possible to definitively establish whether or not the level of contamination is harmful.
Professor Boobis admits there are "gaps in the data". He told Tonight that his Committee made proposals in 2013 outlining potential further research but neither the government nor the regulator ever responded.
British Airways said: “The evidence does not support the conclusion that there is a risk that future deaths will occur unless action is taken.”
“The most recent example of such advice may be found in the Committee on Toxicity position paper on cabin air in 2013.”
Richard Westgate's coroner has not yet concluded his investigation. The inquest is set to open at the end of this year. Sheriff Stanhope Payne will assess the scientific evidence and there's a lot hanging on the outcome.
A verdict of "death by industrial disease" would vindicate the Westgate family's belief that Richard died, in part, because of the job he did. It could also lead to changes to the way aircraft are designed and built and it would open the door to compensation claims by those affected.
Tonight: How safe is your cabin air? will be broadcast on ITV at 7.30pm