ATLANTA — Delta Air Lines Inc., the last U.S. full-fare carrier without a fee to check a traveler's first bag, will start charging $15 for the service as it works to boost revenue.

The move takes effect for flights on or after Dec. 5, Delta said yesterday in a statement. Checking a second bag will cost $25, half the current rate. Delta became the world's largest carrier by closing its purchase of Northwest Airlines Corp. last week.

The fee reverses Delta's earlier plan to keep the first bag free, and is among its initial moves to match Northwest's pricing for certain services. Atlanta-based Delta said Oct. 29 it was adopting Northwest's policy of offering coach seats with more legroom, such as those in exit rows, for $5 to $25 extra.

Delta also is switching to Northwest's prices for reserving tickets by phone by reducing the fee to $20, from $25. A $3 fee for curbside check-in will be dropped to align with Northwest's policy, Delta said.

Also being eliminated are fuel surcharges ranging from $25 to $100 for frequent-flier award tickets in the U.S. and Canada for Delta or Northwest flights. Those fees were added earlier this year as jet fuel rose to a record $4.36 a gallon in July. Fuel has since dropped by half.

Southwest Airlines Co., the largest low-fare carrier, doesn't charge for the first two pieces of checked luggage, and has touted that in advertisements on television and on its Web site. JetBlue Airways Corp. and AirTran Holdings Inc. both let passengers check one bag for free.

Delta fell 80 cents to $10.48 yesterday in New York Stock Exchange composite trading.