Sitting in the cabin of the jumbo jet as it headed across the Atlantic, Emily Graeme and her family were looking forward to a fortnight in Florida. Little did they know that their holiday would be wrecked before the plane had even touched down.
'We were halfway through the flight when my six-year-old daughter complained of a funny smell and was then violently sick,' says Emily, 37. Over the next few days, other family members became ill. Emily suffered severe flu-like symptoms and breathing problems.
'I couldn't move. I was wheezing and had lots of crackling in my chest,' she says. 'It was just awful. I really thought something serious was wrong.' At first, she assumed the family was suffering from a virus. But when she arrived at the airport for the flight home her suspicions were roused.
'You can imagine my surprise when I realised other passengers had the same symptoms. I spoke to five, then ten, then 15 other people. I spoke to more than 40 in the end.'
Bemused, on her return home Emily consulted doctors. They told her she was not suffering from a virus or bacterial infection and ruled out food poisoning - the holidaymakers affected had been seated in different parts of the plane and had eaten different meals. Emily had eaten only bread.
So what was the mystery illness? Today, Emily, whose family continue to suffer ill health, is convinced she and her children had fallen victim to what is known as 'aerotoxic syndrome'. The phrase has been coined to describe the illness that results when the air that plane passengers breathe becomes contaminated with a cocktail of chemicals from the aircraft's engines.
Said to affect the body in much the same way that nerve gas does, the consequences of inhalation appear to be instant and long-lasting.