WASHINGTON — Many of the nation's largest airlines have begun giving military personnel on official travel a pass on expensive baggage fees when they carry heavy duffel bags stuffed with combat gear.

Faced with criticism from veterans groups and others that the fees are a financial burden, several airlines have announced exceptions for service members. AirTran Airways, Continental Airlines, Delta Air Lines, Northwest Airlines and United Airlines said Friday they were waiving all or most of their baggage fees for active members of the U.S. military on official travel.

Earlier this week, American Airlines, Alaska Airlines and Horizon Air began waiving their fee to check a third bag for active service members.

Many airlines struggling with the high cost of jet fuel implemented or increased baggage fees this year. Some service members, including those deploying to and from combat zones, have said they've been asked to pay as much as $300 extra for overweight duffel bags that may include body armor and other vital combat equipment.

Veterans of Foreign Wars Commander In Chief George Lisicki sent a letter earlier this month to ATA, the Air Transport Association, which represents the airline industry, asking for a break for service members. On Friday, Sen. Hillary Rodham Clinton, D-N.Y., sent a letter to six major airlines and Defense Secretary Robert Gates asking that airlines that continue to impose baggage fees bill the Pentagon directly rather than have service members pay the fees themselves.

"Members of our armed forces traveling on official orders should not have to bear any cost whatsoever associated with that official travel," Clinton said. "Our men and women in uniform deserve our utmost respect and gratitude, not additional, unnecessary paperwork."

Reps. James Oberstar, D-Minn., chairman of the House Transportation and Infrastructure Committee, and Jerry Costello, D-Ill., its aviation subcommittee chairman, also wrote to Gates and the ATA Friday objecting to extra fees for service members traveling on official orders.

"The current arrangement of filing reimbursement paperwork to recoup costs associated with excess baggage is an undue burden on our servicemen and women who are bravely entering or leaving a combat zone," the congressmen wrote.

David Castelveter, an ATA spokesman, said he expects most airlines to drop or modify their fees for military personnel on official travel.