Travellers retrieve their luggage at the Los Angeles airport in April 2008. But what happens if your bags never arrive on the carousel? (Ric Francis/Associated Press)

Luggage claim can be a nerve-racking experience for travellers. Smiles of relief spread across the faces of those pushing loaded carts away from the carousel, while those left behind at the conveyor belt watch with envy and increasing anxiety.

A man looks for his luggage amid thousands of suitcases after a strike by baggage handlers at Brussels International Airport in August 2008. (Yves Logghe/Associated Press)

Each year, millions of suitcases don't arrive where they should. And that count seems to be rising. According to the Air Transport Users Council, more than 40 million bags were misplaced by airlines in 2007, compared with 30 million bags just two years earlier.

Most lost suitcases find their way to their proper destination within 24 hours. But of the bags lost in 2007, more than one million — or one bag per 2,000 passengers — were never recovered, the council said.

Some of these lost bags sit at airports for months waiting to be claimed, before their contents are finally sold, donated or dumped. What happens to travellers' new cameras and dirty underwear depends on which airline carried the suitcase, and where in the world the plane landed.

The auction block

Bags abandoned at Heathrow Airport are auctioned off at Greasby's in southern London. In the United States, thousands of unclaimed suitcases are unpacked each year and their contents sold at the 40,000-square-foot Unclaimed Baggage Centre in Scottsboro, Ala.

At Canadian airports, each airline is responsible for its unclaimed baggage.

Air Canada and WestJet both have customer service agents at each airport who try to reunite baggage with its owner. After several days, unclaimed bags are sent to the airline's central baggage tracing office. Air Canada sends its bags to Montreal-Trudeau Airport after five days, and WestJet to its hangar in Calgary after three days.

Agents at the central offices then open and search through the luggage for tags, business cards, personal documents, drug prescriptions or anything else that can help identify the owner. If agents can't identify or contact the owner, descriptions of the bag and its contents are entered into a system called WorldTracer, which acts as a lost and found system for over 400 airlines and ground handling companies worldwide by matching bags with claims.

Hope fades after 3 months

Travellers who still haven't located their missing bags after a few months should probably give up hope.

WorldTracer files expire after 90 days, and Transport Canada only requires airlines to hold on to loss claims for three months. After that, Air Canada and WestJet agents unpack the bag and donate usable items such as clothing to local charities and shelters, and dispose of the rest.

Peter Fitzpatrick, spokesperson for Air Canada, says baggage teams rarely resort to throwing out lost luggage. "We do everything we can to find the owners," he says, "because obviously, people want their bags back."

Doris Carreiro-Fonseca, manager of WestJet's central baggage services team, also says most bags find their way home. Since January 2008, only one bag has sat unclaimed for more than 90 days, she says, "and we're still working to find its owner."

Cost of $3.8 billion

Flight connections pose the biggest problem — transfers from one aircraft to another accounted for almost half the bags that were missing on arrival in 2007.

Mishandled baggage cost airlines and airports $3.8 billion last year.

Years ago, the Unclaimed Luggage and Goods Boutique in downtown Ottawa helped find new owners for unclaimed bags. But the store has moved several times in the past decade, and if it still exists, its current location is a secret well kept by bargain hunters.