It is extremely worrying that so many people could be developing these life-threatening conditions and not even be aware of it

John Smith MP

At their first meeting on Wednesday, MPs heard that as many as one-in-ten people could develop potentially fatal blood clots by remaining seated throughout long-haul flights.

They called for immediate research into the problem, after being told by a medical expert that the absence of immediate symptoms made it difficult for doctors to link DVT with air travel.

Consultant surgeon John Scurr, of Stamford Hospital in London, told MPs that despite the lack of symptoms, 40% of those affected developed life-threatening clots that required immediate treatment.

Fatal consequences

More than 40 long-haul airline passengers have died from DVT clots.

They include Emma Christoffersen, from Newport, Susan Mavir-Ross, from Llay in Wrexham, Thomas Lamb, from Cardiff, and John Thomas from Cowbridge, south Wales.

Emma Christoffersen died after a long-haul flight from Australia

Solicitors representing nearly 300 claimants went to the High Court in London in January to launch legal proceedings against 30 major airlines.

Medical research has shown that clots develop in blood vessels deep in the legs when circulation slows - when people remain seated for long periods, for example.

The clots can prove fatal if they break off and are carried to the lungs, blocking the flow of blood.

Several medical reports have claimed a link between DVT and air travel, although it is yet to be proved.

Inquiry calls

Mr Smith - whose constituency includes Cardiff International Airport - said the fact that victims showed no symptoms was a cause for concern.

"It is extremely worrying that so many people could be developing these life-threatening conditions and not even be aware of it.

MP John Smith calls for more research

He added: "If you consider that it takes between five and nine days for clots to develop, and then travel to the lungs or the heart, it is little wonder that so few DVTs are linked directly with air travel as doctors are not required to seek any connection.

"This is all the more reason why research should be undertaken immediately."

In January, campaigners staged a candlelit vigil outside the House of Commons demanding a public inquiry into the health risks of air travel.

UK Transport Minister John Spellar said the government would participate in a World Health Organisation study into DVT cases, but stopped short of announcing a separate inquiry in Britain.