The A350-900 is designed to compete with Boeing 777 and 787 jets in the lucrative long-haul segment and has already received 750 orders.
Equipped with Trent XWB engines from Rolls-Royce, the plane can transport 315 passengers up to 14,500 kilometres (9,000 miles).
Delta already has a sizable fleet of Airbus aircraft, with 126 single-aisle medium-haul A320s and 32 A330s. It has recently made orders for another 55 Airbus planes.
Aerospace analyst Christophe Menard said that Airbus likely benefitted from the fact that it could deliver A350s rather quickly after Emirates cancelled in June an order for 70 of the aircraft.
"Boeing, on the contrary, doesn't have quick slots available for its 787," he said.
Westhouse Securities said in a note to investors that the order indicates that the delivery date is becoming a crucial factor for airlines.
Copyright Agence France-Presse, 2014