Dialogue: And you mightn't even feel a thing

Apparently the class system is alive and well and is now defined less by manners and more by means. It still has a lot to do with blood, though, but doesn't discriminate between blue and ordinary red.

Economy class syndrome, or deep vein thrombosis, is thought to result from sitting immobile on long flights, whereupon big blood clots can form in the legs. Reports claim that because of the cramped conditions in cattle class, restricted movement and, perhaps, too much alcohol, people are suffering from clots that, while not always fatal, do have the potential to kill.

The economy aspect of the name is a bit of a misnomer. The most recent findings reveal that first and business-class passengers are just as likely to suffer. That's a relief - at least those of us down the back of the plane won't have to worry about whether to shell out for more expensive seats.

Interestingly, the first study about the risks associated with flying was published in 1940 but airlines preferred to protect their interests and kept the matter to themselves.

Airline executives, who are said to have known about the relationship between long-haul travel and pulmonary embolisms, argue that inactivity on planes is no more hazardous than sitting still for long periods in a car or on a train.

I might have been completely satisfied with that claim had it not been for a Norwegian study that found that, as a result of the drop in air pressure during fights, the likelihood of clotting was increased in flight.

The cat really came out of the bag in October when a young woman died after stepping off a flight from Australia. The media covered her death at some length.

Ann Egerton, a survivor of a huge post-flight clot, says it makes her really angry that these risks had been known about for so long yet so little had been done to prevent needless fatalities. The truth is, she says, that while flying you are more likely to die from a blood clot than a plane crash.

Whether that's true or not, reports on economy-class syndrome gained further momentum when a group of English health professionals went public with their suspicions that hundreds of people are dying every year from clots caused by flying. Doctors at a hospital near Heathrow claim they see several cases each week and have reported 30 deaths in three years. A third of the dead had flown from Australia in economy seats.

People over 50 are believed to be more likely to suffer, but that didn't stop three British Olympic coaches from getting blood clots when they flew to Sydney for the Games. The vascular surgeon who treated them commented that if it can happen to people in such good health it can happen to anyone if the right conditions exist.

Naturally, I wanted to know how to find out if there was a timebomb ticking in my veins. I called a doctor and she told me, completely for free, that a person might suffer some slight swelling and minor to excruciating pain. But, then again, one might not feel a thing. Hmmm, I don't know if that makes me feel any better about flying.

The good news is there are things you can do to prevent clotting. Aspirin can reduce the risks and walking about during the flight or even just wriggling your toes may help keep you safe. Drinking plenty of water is also meant to minimise harm. But, be warned - Britain's Public Health Laboratories say that 15 per cent of water fountains on planes using major British airports are contaminated with e-coli and excrement. Might pay to take bottled water as well.

I then had what I thought was a brilliant idea which involved all passengers on long-haul flights being encouraged to do the chicken dance or the hokey-tokey between courses and before movies.

When I suggested this to friends, they told me it wouldn't work because airlines don't want all the passengers moving around at once, apparently because it it could upset the plane. I'm not sure if anyone has ever put that to the test - it might be just an airborne myth.

But if you thought the only risks when flying came from crashing, terrorism, fellow passengers losing the plot, or the airline losing your luggage, then think again - it seems there are all sorts of danger lurking up there in the sky.