Delta Air Lines has placed an order for 50 Airbus aircraft to replace its older Boeing fleet.
The deal, worth $14 billion (£8.9 billion) at list prices, is for 25 A350-900, and 25 A330-900neo planes.
The Airbus jets will replace the US carrier's ageing B747 and B767 aircraft with the A350s due to start arriving in 2017 and the A330s from 2019.
Delta said it plans to operate the A350s on long-range routes between the US and Asia and that they will provide a "20 per cent improvement in operating cost per seat compared to the B747-400 aircraft they will replace".
The carrier will roster the A330s on medium-haul transatlantic routes and select services between the US west coast and Asia. It again said these aircraft will deliver a 20 per cent operating cost saving per seat over the B767-300s they will replace.
Both Airbus aircraft will feature Rolls-Royce Trent engines.
Nat Pieper, Delta's vice president of fleet Strategy and transactions, said: "Delta always approaches fleet decisions with a balance of economic efficiency, customer experience enhancements, network integration and total cost of ownership.
"The A350 and A330neo support our long-haul, transoceanic strategy and join a mix of Boeing and Airbus aircraft that provide exceptional flexibility for Delta's global network as well as strong cash-on-cash returns for our shareholders."
Delta last week announced it will next summer fly up to 11 weekly flights between New York JFK and Athens (see news, November 14).