Australia's two top airlines are to print health warnings on their tickets about the danger of blood clots to long haul passangers.
Qantas and Ansett will increase the warnings given to passengers about the risk of deep vein thrombosis - known as "economy class syndrome".
A Melbourne law firm is preparing to file compensation claims for more than 800 people who say they have suffered deep vein thrombosis during flights. The condition can be caused by sitting still for long period.
Ansett is also producing an in-flight video giving passengers advice on the problem, and an article is due to be posted on the airline's website from next week.
British Airways, which owns 25% of Qantas, is also issuing recommendations to passengers on how to avoid blood clots during flights.
The company's health warnings will advise long-haul passengers to wear loose clothing, eat light meals and avoid drinking too much alcohol to lessen the risk of potentially fatal blood clots.
The lawsuit by Melbourne firm Slater and Gordon will target most major airlines, including British Airways, Qantas, Japan Airlines, Air Canada, Air France and Singapore Airways, a spokesman said.