A Canadian man is urging airlines to "take a good hard look at what they're doing" after he revealed a cramped flight nearly killed him.
Cyclist and marathon runner Colin Savage, 64, said he was on an Air Canada flight from Chile to Toronto when turbulence forced passengers to stay seated for most of the flight.
But this was far from ideal for Savage, who is about 188cm tall and was forced to spend most of the 10-hour flight pressed up against the seat in front of him due to limited legroom.
"In their seats, my knees were up against the seat in front of me. I was constantly squirming around trying to get comfortable," he told Canada's CBC News.
About two days after he returned home to Victoria, British Columbia, Savage said he felt "horrible" pain in his lower back and went to a doctor.
He was told he had deep vein thrombosis (DVT) and that blood clots had moved their way up his legs and into his lungs, nearly killing him.
Savage said he was now constantly short of breath and his general fitness was in decline.
"I have much less energy because I can't take a lot of oxygen in," he said.
"I'm shuffling around like a senior.
"Doctors in hospital emergency told me that I nearly lost my life."
DVT occurs when a blood clot develops within a deep vein, usually in the thigh or leg. It can break off and make its way to the lungs.
According to the World Health Organisation, passengers travelling in cramped areas for more than four hours are at risk of developing DVT.
A Dutch study in 2007 found air travellers taller than 185cm and shorter than 165cm had a higher risk of DVT after air travel compared to those within the same height range.
An inquest in the UK in April found a British Airways pilot died as a result of DVT a day after piloting a flight from Shanghai, China.
And many airlines offer in-flight information for passengers on how to avoid DVT during their flight.
But when Savage raised his DVT troubles with Air Canada, the airline brushed aside his concerns.
"Medical evidence has shown that deep vein thrombosis (DVT) is the result of a pre-existing personal medical condition, related to an individual rather than a transportation system," the airline told Savage in a statement.
"International courts have confirmed that based on the aforementioned evidence there is no liability to air carriers for DVT that occurs during a flight."
Air Canada told CBC News there was no conclusive medical evidence specifically linking DVT with flying.
James Douketis, director of vascular medicine at St Joseph's Healthcare in Hamilton, Canada, told CBC there have been a lot of studies examining the link between DVT and flying, but they hadn't been done very well.
"Most are not what we call methodologically rigorous or of a high scientific standard. What that means is, it makes a lot of the results murky," he said.
"We do know that airline travel increases your risk of blood clots. We know that the longer you travel the higher the risk, and we know that if you have predispositions - like recent surgeries or previous blood clots - your risk is highest."
Savage's ordeal has again raised the issue of legroom for passengers on planes - also known as seat pitch - as airlines squeeze more and more seats on flights.
A recent comparison of seat pitch on six popular carriers flying in and out of Australia by Skyscanner found United Airlines was the most generous at almost 94cm. At the other end of the scale, Qantas' fleet had a seat pitch of just under 79cm.
Meanwhile, airline seats themselves are shrinking - in April, a Bill in the US that would have set size standards for airlines seats was voted down, meaning seats can continue to shrink.
Savage said he was slowly recovering but said airlines needed to reconsider the conditions on flights.
"The airlines need to take a good hard look at what they're doing and the (Canadian) government needs to lead them in that direction," he said.
According to the Australia and New Zealand Working Party on the Management and Prevention of Venous Thromboembolism (VTE; a condition that includes DVT), passengers can minimise their risk of developing travel-related VTE with the following suggestions:
• Staying hydrated by drinking sufficient fluids
• Regularly move and use ankles, massage calves and exercise legs
• Avoid combining sedatives with excess alcohol
• Wear loose, nonrestrictive clothing
• Exercise, such as walk, before and after travel and during stopovers.
The surgeons on the working party said passengers most at risk of VTE were those with a history of the condition, other significant medical conditions and those who had recent surgery.