From cellphones to prosthetic limbs, passengers have a habit of leaving everything imaginable behind on airplanes and at airports, forcing some airports and airlines to put systems in place to try to reunite lost items with their owners.
Earlier this year, the situation became so unmanageable for Southwest Airlines that the airline launched its own sophisticated computer software to match travelers with their wayward belongings.
"It really is mind-boggling the amount of things that are coming through," said Robert Lehr, manager of baggage services for Southwest. "The volumes are just staggering.
"Basically, if you can carry it on a plane, it's been left on a plane."
And during the holidays -- the busiest travel time of the year, when airports and airplanes are packed with stressed people -- it stands to reason that even more stuff shows up on the lost-and-found pile.
But it's not just air travel. People tend to lose more items in December than at any other time of the year, according to survey numbers released this month by electronic data backup firm Mozy.
"The times when people are busy and moving around a lot cause peaks in loss, so it may come as no surprise that 6 p.m. on Fridays and Saturdays in December are relatively disastrous when it comes to hanging on to your things," Mozy said in a statement announcing the survey results.
Anecdotal evidence would seem to back that up.
On Dec. 14, a Friday, Southwest had 28 Apple iPad tablet computers turned in to lost and found across its flight system, Lehr said. It flies about 3,800 domestic flights each day.
The Mozy survey showed that 39.5 percent of Americans lose two or more belongings a year. The survey also showed that the average American misplaced nearly $250 worth of possessions in the past 12 months. That adds up to more than $30 billion of lost property this year.
While December is ground zero, the tendency to lose things is year-round.
Southwest typically gets 10,000 to 13,000 items turned in to lost and found every month. That's 120,000 to 156,000 items a year. The airline has a warehouse devoted to nothing but storing and cataloging things that have been left on its airplanes.
"By and large, it's mostly electronic items," Lehr said. "We get tons of cellphones."
It's not just high-end electronics that are left behind, though.
"Reading glasses we just get thousands of, just crazy amounts," Lehr said.
Seat-back pockets are trouble
Seat-back pockets are the black holes of aircraft. All sorts of things are left behind in those pouches. It's so bad that Southwest has adopted see-through plastic mesh for seat-back pockets as part of the redesign of its aircraft interiors, Lehr said.
Travelers aren't just leaving things on airplanes.
Milwaukee's Mitchell International Airport sees thousands of items that are left behind by travelers each year. The airport has a team of volunteers who deal with lost and found items at the airport.
The list of items left behind is long and ranges from mundane (paperback books) to head-scratching (oxygen tanks).
Lost and found items at the airport include sunglasses -- cheap, designer and prescription -- jewelry, clothing, car seats, strollers, mittens, gloves, credit cards, passports and car keys.
Volunteers are often left to wonder how folks managed to continue on their journey without their crutches, wheelchairs or oxygen tanks.
Southwest also has its share of head-scratchers. "A prosthetic leg was left on a plane," Lehr said. "A prosthetic limb, we would think they'd want it back pretty badly."
Southwest has a team of employees who do nothing but handle lost and found items.
"These are people's possessions, and someone had that pit-of-the-stomach feeling with every one of these things," Lehr said. "We have to do everything we can to get the items back to their owners."