Flight attendants often say that the biggest messes they have to deal with are dirty diapers left in seat-back pockets or worse, handed to them while they are serving beverages and snacks. "Would you hand that off to your server at a restaurant?" said Corey Caldwell, a spokeswoman for the Association of Flight Attendants, a union representing workers at several big airlines. "It's amazing how people treat the inside of aircraft cabins as opposed to other public spaces."

The detritus problem is exacerbated by the fact that most airplanes are only lightly cleaned between each flight. Airlines say planes get a more thorough cleaning overnight and a "deep cleaning" scheduled about every 30 days. In many cases, seat-back pockets aren't thoroughly checked until overnight cleaning crews work over a cabin.

At several airlines, including Southwest Airlines Co., flight attendants handle most of the cleanup between flights. AMR Corp.'s American Airlines and UAL Corp.'s United Airlines have cleaning crews pick up trash, fold blankets and replenish supplies between flights. United says its crews brush off seats and replace headsets, too, between flights.

Eric Kaldenberg, a Phoenix regional sales manager, was on a flight home from Las Vegas in March with a passionate couple in first class who were anything but discreet.

"It was pretty disgusting," Kaldenberg said. He says he and other first-class passengers complained to flight attendants, but no action was taken. He wrote to US Airways, which offered a form-letter apology and voucher for a discount on a future ticket, along with a suggestion that he could have asked to be reseated if the couple bothered him. "I regret your discomfort when observing inappropriate behavior of another passenger," US Airways' Customer Relations office said in the letter. His second complaint drew an apologetic phone call from a customer-service supervisor, he says. US Airways' Gee says the suggestion that Kaldenberg should be reseated "probably wasn't the correct response." The flight attendant involved "should have talked to the couple," he said.

While some people are testing boundaries or acting out when away from spouses, friends or seemingly any authority, experts say that for others, air travel leaves people psychologically off-kilter and more likely to do things they wouldn't normally do. Some lose control because the flying experience strips them of all control — you're told where to sit, when to sit and when you will arrive.