Passengers on U.S. airlines reported more than 4 million mishandled bags last year as overall consumer complaints were up even though the financial performance of major carriers improved.

Transportation Department figures released on Wednesday show domestic airlines flew more than 600 million passengers who checked luggage in 2006, and mishandled 4.08 million bags. This includes luggage that was lost, damaged or placed on the wrong aircraft.

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The industry's mishandled bag rate was 6.73 per 1,000 passengers, up slightly from the previous year, when 440 million passengers checked luggage and 2.93 million bags were mishandled, government figures show.

Southwest Airlines (LUV) flew more than 98 million passengers last year — the most of any U.S. airline — and mishandled more than 525,000 bags. US Airways flew about half as many passengers and mishandled more than 420,000 bags.

Bankrupt Delta Air Lines flew 66 million passengers and mishandled 456,000 bags. Northwest Airlines flew 46 million passengers and mishandled 212,000 bags.

Major carriers did better overall than their regional counterparts, based on the number of passengers each flew. Several regionals, including Comair, which flies for Delta, and American Eagle, which flies for American Airlines , registered mishandled bag rates per 1,000 passengers in double-digits.

Overall consumer complaints against the airlines, which are reported separately from bag problems, totaled 5,746 last year, up by 314 from the previous year.

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