The airline says it will also fly to Halifax any relatives of the 215 dead passengers who wish to go.

"We have decided to make an immediate payment to the families of victims, although that does not normally happen in the industry. We will transfer $20,000 to anyone who desires this," says Philippe Bruggisser, chief executive of Swissair parent company SAirGroup.

"Of course we are liable for much more, we know that, but this is an initial, immediate measure so that money is available for travel and the inconvenience," Mr Bruggisser told a late-night news conference at Zurich airport on Thursday.

Mr Bruggisser repeated steps Swissair had taken and would take to help relatives of people killed in Switzerland's worst aviation disaster.

"We had always planned for such a case but we always thought it would not happen. Now we have to see it can happen," he said.

However, correspondents say the offer surprised legal observers who felt it was only the beginning of what is expected to be a long and costly legal battle over compensation from Swissair.