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 Wednesday 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 last week that it was adopting Northwest's policy of offering coach seats with more legroom, such as those in exit rows, for $5 to $25 extra.