Airline passengers whose claims for compensation for deep vein thrombosis (DVT) were rejected by the high court last year asked the court of appeal yesterday to overturn the earlier ruling.

On the same day their claims were thrown out last December, a court in Australia gave the go-ahead for 400 claims to proceed there, three senior appeal court judges were told.

Claims are being brought against 18 airlines by survivors of DVT and relatives of those who have died. The original 50 claimants have dwindled to 24 because the others "did not have the funding to continue", the claimants' counsel, Stuart Cakebread, told the court.

The key question in the case is whether DVT counts as an "accident" under the 1929 Warsaw convention, which limits airlines' liability to passengers. DVT, also dubbed "economy class syndrome", is a blood clot, usually in the leg, which can develop when movement is restricted for some time. It can be fatal if the clot reaches the lungs or brain.

Those who died include Emma Christoffersen, 28, from Newport, south Wales, who died from a blood clot after sitting for 20 hours on a flight from Australia to Britain in October 2000. Neil Wilson, 32, from Wigan, died in January last year, nine hours after flying to Spain.

Mr Cakebread told the master of the rolls, Lord Phillips, and Lords Justice Judge and Kay that the claimants were asking them to take the same approach as the judge in Australia. It was the claimants' case that "a cause of the DVT was an 'accident' within the meaning of article 17 of the Warsaw convention".

The "accident" was constituted by a number of factors - the method of operation of the flight and the "failure by the relevant carrier to warn the passenger of the danger posed by the flight and to advise the passenger so that he or she could take appropriate steps to minimise or eliminate the danger of suffering a DVT".

The hearing continues.