As thousands prepare to jet off on holiday this summer, Joel Hills investigates growing concerns over air quality on board passenger aeroplanes. After the autopsies of a pilot and an air steward revealed toxic levels of organophosphates in their systems, a British coroner predicted further casualties unless action is taken, and called for a re-evaluation of the science around testing cabin air toxicity. This programme examines the evidence and speaks exclusively to the family and friends of those who have died.