http://blog.wired.com/cars/2008/10/airplanes-becom.html

Handing over two bucks for a can of Coke on a long flight is depressing, but it's even more so when you place that soda on a tray table that's covered with a giant advertisement.
It's a bummer, but it's becoming more and more common. Airlines, eager to grab revenue anywhere they can get it, are opening up every square inch of their planes to advertisers, selling space on tray tables, walls, overhead bins, soap dispensers, cocktail napkins and barf bags. If the idea proves successful, it could generate millions of dollars in new revenue.