Delta Air Lines said on Thursday it will create a class of higher-end coach seats on its U.S. fleet, matching a service it already offers on the bigger planes that fly overseas.

Delta is calling the seats "Economy Comfort." They're regular coach seats with an extra three inches of legroom. Travelers in those seats get to board the plane sooner, too. Delta will start selling them as US$19 to US$99 add-ons to the price of the ticket. Delta didn't say how much it will charge once the introductory period ends. Similar seats on Delta's overseas flights sell for US$80 to US$160.

Delta is creating the extra legroom in the first three to five rows by removing what it called a "negligible number of seats" from each plane. It expects to have its whole mainline fleet done by next summer.

The seats are similar to a United Airlines offering called "Economy Plus". Those seats have been considered a big success because some passengers are willing to pay for more legroom, but won't pay for business class. United's parent company, United Continental Holdings Inc., has said it will put similar seats on planes that had been owned by Continental as it merges the two airlines.

Shares of Delta Air Lines Inc. rose 15 cents to US$8.65 in afternoon trading.