The sooner we get this action properly constituted within the framework of a group litigation order the better because time is passing

Master Turner, High Court

The claimants argue that a combination of cramped flying conditions and long hours in the air give rise to the condition, also known as economy class syndrome.

World airlines say there is no definitive proof linking DVT to air travel, but some have agreed to help a World Health Organisation study into whether a link exists.

Potential claimants

Lawyers said 286 potential claimants had come forward and contacted solicitors.

One of them is Lyn Walcott from Essex, whose husband Nigel died after travelling on a BA flight from Barbados in October 2000.

High Court official Master Turner said the claimants could pursue their group litigation order, subject to approval by the Lord Chief Justice Lord Woolf.

He said: "The sooner we get this action properly constituted within the framework of a group litigation order the better because time is passing."

The legal battle is due to begin later this year.

More space needed

Meanwhile, it has emerged that people may need more space on airplanes because they are getting taller and fatter.

Lord Falconer said people were getting bigger

The finding was disclosed by Transport Minister Lord Falconer in written response to a plea for an increase in the minimum space between rows of seats for airline economy class travellers.

He told Lord Morris of Manchester that Civil Aviation Authority regulations required UK-registered aircraft to have a minimum distance of 26 inches between the back support cushion of a seat and the back of the seat in front.

But he added: "A recent study, aimed principally at harmonising European standards in this area, found that in view of the increased height and weight of the population, there should be an increase in seat spacing.

"The Joint Aviation Authorities are considering its recommendations."

Lord Morris said: "Because of the danger of deep vein thrombosis, coupled with the fact that we are all now, apparently getting taller and fatter, there is an urgent need for this minimum distance to be increased.

"Sometimes people have to spend upwards of 20 hours in these cramped conditions.

"I shall be pressing for them to get a move on."