ATLANTA (AP) — Delta Air Lines said Monday that it made a deal with ticket distributor Travelport that will allow travel agents to sell its "Economy Comfort" seats.

Those are coach seats with extra legroom. Delta has been selling them on its website and its reservations centers for an extra charge of $19 to $99 above the regular fare for the seat.

Under the deal, travel agents who use Travelport's Galileo, Worldspan or Apollo reservations systems will be able to sell "Economy Comfort" seats later this year.

Airlines have been tangling with distributors over about selling add-ons like checked baggage, upgraded seats, and onboard internet access.

Global distribution systems such as Travelport are a significant distributor of airline tickets, especially to travel agents and corporate travel offices. Both sides have said they want to those add-ons in the global distribution systems, although agreeing on terms has been another matter.

Delta said the Travelport deal is its largest yet for add-on services.

Privately held Travelport and Delta are both based in Atlanta.

Shares of Delta Air Lines Inc. fell $1.31, or 11.4 percent, to $10.20 in Monday afternoon trading, after the airline said a key measure of its May revenue came in lower than it expected.