Economy-class syndrome, a condition caused by blood clots, may kill more than one air passenger a month in Britain, according to a doctor at the hospital closest to London's Heathrow Airport.
The hospital has seen 30 deaths from the condition in the past three years, a study carried out by an accident and emergency consultant employed there has shown.
Economy-class syndrome is caused by blood clots developing in the legs as travellers sit in the same, often cramped position for hours on long-haul flights. The blood clots cause deep-vein thrombosis, and in some cases the clots travel up to the lungs, causing potentially fatal pulmonary embolism.
Ashford Hospital in Surrey, the hospital closest to London Heathrow, often treats passengers who collapse there. Consultant Mr John Belstead said his research showed there had been 30 deaths in the past three years at the hospital among patients who had had pulmonary embolism within minutes of getting off long-haul flights.
A spate of deaths from the condition recently prompted a British House of Lords report, which concluded that more investigation was needed into the causes of the syndrome.
Research at Tokyo international airport's clinic meanwhile has found that in the past eight years, 25 passengers arriving there have died from blood clots and circulatory problems.
Every year doctors at the airport treat between 100 and 150 passengers suffering from the syndrome, said Mr Toshiro Makino, director of the clinic.
"The biggest problem is dehydration, and that is made worse by drinking alcohol. My advice is to keep off the alcohol and drink lots of water," Mr Makino said.
Many of the victims were middle-aged or elderly, with the average age of those who died being 64, the research published in the latest edition of New Scientist revealed.
Despite the syndrome's colloquial name based on its link with cramped conditions in economy class, it does not just strike economy-class travellers. One victim was an airline pilot who collapsed after a flight from the US.
British Airways announced this week that it is to print warnings about the syndrome on airline tickets.