David Beckham's commute from Los Angeles to London could have a career-threatening effect on his health, according to experts.
Beckham was England's man-of-the-match against Estonia
Beckham will clock up thousands of air miles if he continues to play for England while with the LA Galaxy.
And aviation health expert Farrol Kahn warned: "It puts him in the high risk category for getting deep-vein thrombosis (DVT).
"That would ruin that leg for life - you simply could not use it again."
Beckham will also struggle to be at his physical and mental peak for England and Galaxy games in the immediate aftermath of long flights, according to Kahn.
Kahn told BBC Sport: "They've done studies of rapid deployment forces in the US military who have to fly long distances and then fight.
You are seven times more likely to catch a cold if you fly than if you don't
Aviation health expert Farrol Kahn
"In these young males, sprint times were reduced by 10%, lift and carry tasks by 9% and logical reasoning skills by 15%."
Beckham's England commitments alone could see him spending around 200 hours in the air before next summer's European Championships.
That's in addition to the thousands of miles he will also cover flying to away matches in New York, Washington and New England with the Galaxy and those he will make for personal reasons.
And that amount of flying will also leave him far more susceptible to disease.
Kahn said: "Research has shown that you are seven times more likely to catch a cold if you fly than if you don't.
Beckham's LA-London commute is unparalleled in England history
"On most modern planes, 50% of the air is recycled, which circulates viruses around the cabin.
"Viruses also tend to love dry air. Bacteria love damp conditions, but viruses proliferate in dry air.
"In a normal office, relative humidity is about 60%. In an aircraft cabin it's a third of that."
Studies by the World Health Organisation have previously highlighted the risks of deep-vein thrombosis to long-haul flyers.
Kahn said: "We first thought that DVT was mainly a problem for the elderly, but we're increasingly finding that it can occur to people much younger.
"If an athlete has an injury to the lower leg, that increases their chances of getting DVT.
"If a footballer has been kicked, so they have a bruise or internal haemorrhage, that increases the chances.
"If a librarian were to get a DVT, she wouldn't be able to stand up to do her job - she just wouldn't be able to put any pressure on that leg."
Beckham is expected to remain part of England coach Steve McClaren's plans for the foreseeable future after a successful return to international football in the past.
Beckham supplied the cross that led to England's solitary goal against Brazil last Friday, and was named man-of-the-match against Estonia on Wednesday after setting up two of his side's three goals.