American Airlines Inc., the last holdout among major U.S. network carriers, announced Monday that it will begin charging its coach passengers $25 if they check a second bag.

American said it would begin assessing the fee for economy-class tickets bought on or after May 12. Passengers who buy non-discounted tickets or are premium members of its frequent-flier program won’t get hit with the charge.

American said the new fee was intended to “account for the rising costs associated with the transportation of checked baggage, including the price of fuel.”

After United Airlines Inc. announced the new fee in early February, US Airways Inc., Northwest Airlines Inc., Continental Airlines Inc. and Delta Air Lines Inc. said they too would impose fees for second bags for travel beginning May 5.

American said it expects its fee, which also applies to American Eagle passengers, would hit about 4 percent of its domestic passengers who check more than one bag. The others would be exempted.

American didn’t estimate how much it expects to raise with the new fee. United has said it expects the bag charge to bring it more than $100 million annually.

The charge applies to travelers within the United States, Canada and U.S. territories, such as Puerto Rico and the U.S. Virgin Islands, American said. It otherwise does not apply to international travel.

Carriers have adopted a number of new fees and charges in recent months as they try to increase revenues enough to counter the rising fuel prices.

The nation’s 10 largest carriers lost more than $1.7 billion in the first quarter after spending $2.5 billion more for jet fuel in the quarter than a year earlier. Including $10 billion in special charges at Delta and Northwest, the total net losses were nearly $11.8 billion.