The parents of a south Wales woman who died from deep vein thrombosis (DVT) after a long-haul flight are to hold a week-long campaign at Britain's busiest airport.

The event at Heathrow Airport is part of Healthy Flying week and is aimed at making airlines do more to prevent further deaths from what has been dubbed "Economy Class Syndrome".

DVT victim Emma Christoffersen, 28

Ruth and John Christoffersen, from Newport, south Wales, lost their 28-year-old daughter Emma to DVT.

They have joined the campaign, which is seeking to persuade air operators to conduct research into DVT.

The condition has been seen repeatedly in air travellers, though scientists remain divided as to whether there is a definite link.

Emma Christoffersen's family are hoping that the campaign will highlight the dangers of DVT.

'Responsibility'

Mrs Christoffersen, 54, said: "We will be going down to Heathrow and holding a vigil which we hope will last a week.

"We are going to make the airlines listen - they have a responsibility to make sure people are safe and well-informed about DVT.

"It will be the second anniversary of my daughter's death and I would like it to mean something."

Mrs Christoffersen's daughter collapsed and died shortly after arriving back in the UK from Australia after a 20-hour flight two years ago.

MP John Smith has campaigned for action

The fitness fan complained of feeling unwell within minutes of the Qantas Jumbo touching down at Heathrow.

She lost consciousness in the arrivals hall and died before reaching hospital.

Relatives of DVT victims who developed the illness after air travel are calling on the European Parliament to ensure airlines provide better information for passengers.

The campaigners say that passengers should be better informed about the condition.

They want the EU to introduce legislation obliging airlines to provide:

• pre-takeoff health briefings for all flights, similar to the compulsory on-board safety briefings
• DVT information - particularly on preventive action - on airline tickets
• passenger information on the percentage degree of seat pitch in economy class

They also want EU funds to be allocated to research projects assessing the health risks from DVT, particularly on long-haul flights.

In June, Mrs Christoffersen flew to the European Parliament - the first time she had taken a plane following her daughter's death - to call for action.

Her move followed the World Health Organisation agreeing in May to a �1.2m study into the condition.

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

Medical research has shown that clots develop in blood vessels deep in the legs when circulation slows.

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