Travelers are being tapped by the four largest travel distribution companies to donate money to fight diseases around the world. It began as an initiative of former president Bill Clinton and administered by Unitaid, and involves, ahem, a small airline ticket tax.

The program began in 2006 in France, and since then more than $600 million has been raised “with no economic distortion for the airline industry.”  That’s because the $1 or 2 tax is simply folded into the ticket price that’s levied in eight European countries.

A new component is now being developed,by Amadeus which would be voluntary and hassle free. Experts say that this additional source of revenue could balloon to $1 billion a year by 2011. By the time the solidarity levy was conceived, the Clinton Foundation–which now serves as Unitaid’s purchasing agent–“had lowered the price of pediatric medicine from $600 to $190,”

Clinton told NBTA delegates. “But because of their money, because of people getting on an airplane at Orly Airport [in Paris] or some other place in France, and because two dozen other countries kicked in more modest sums, we were able to get the price down to $60. Two-thirds of all the kids in the world today who [require] medicine to stay alive, who through no fault of their own have AIDS, are alive because of this program.”