Researchers have spoken to 10 New Zealanders who claim their relatives died from blood clots after long plane flights.
And an Australian law firm has revealed that 116 New Zealand residents have asked it about taking legal action for travel-related clotting.
The revelations come four days into a recruitmentdrive at Auckland and Wellington Airports to find 1000 people for a study into traveller's thrombosis, or "economy-class syndrome".
After spending 13 hours a day at each airport, medical researchers found 10 people who said their relatives died from travel clotting and 20 who had suffered from the condition.
One, Auckland company director Sandra Reid, said she was put in hospital once in Australia and visited New Zealand emergency wards three or four times after a series of long flights in the Pacific and Asia in 1998.
The 45-year-old said doctors scanned her lungs and found several dangerously large clots. She spent eight months taking blood thinners.
Every time she flies, she now has an anti-clotting injection, wears support stockings and "moves around the plane religiously".
Aucklander Mike Graham, aged 50, said his 77-year-old mother, Joan Graham, flew to Zimbabwe via Brisbane. Twelve hours later she was dead.
"My sister got up, took her some tea and found her lying on the floor. She died five minutes later."
The blood-clot study is by Auckland's Green Lane Hospital and Otago University's Wellington School of Medicine and Health Sciences.
Project leader Dr Rodney Hughes said 350 volunteers had been found so far. They would have blood tests before and after flights.
Dr Hughes said that the term economy-class syndrome was a misnomer. Some people asked to volunteer thought they were fine because they were flying business class.
Australian lawyers at Slater and Gordon, who are taking action for 800 alleged clot sufferers, said they had been approached by 116 New Zealand residents who wanted to take part.
But spokesman Andrew Taylor said his firm would act only for people whose flights had "sufficient connection with Australia".
The Australians have passed dozens of names to Wellington firm Johnston Lawrence.
A lawyer there, Caroline Hannan, said 40 people had been sent legal packages. But the deadline for sufferers to take action was two years.
