US Airways says advertising on tray tables and other places has helped to bring in $20 million, and experts are predicting that other cash-strapped airlines could soon follow suit -- and then some. "Every one of those overhead bins could have an ad -- I don't think anything is sacrosanct," says Harlan Platt, a finance professor at Northeastern University. "It's all about taking advantage of an asset." Airlines, however, are sounding a slightly more cautious note. "We decided against ads on the overhead bins because we don't want to detract from the brand experience," says Tad Hutcheson, vice president of marketing and sales at AirTran Airways. "We don't want (the plane) to look like a subway."