France, Jan. 29 -- Delta Air Lines has placed a firm order for 31 latest generation aircraft including 16 A330-900s and 15 A350-900s. Once delivered, Delta's widebody fleet will have grown to 55 A330neo and 79 A350s. Delta Air Lines currently operates more than 500 Airbus aircraft from all of the Airbus product families from the A220 to the A350-900. Delta Air Lines' current Airbus backlog is around 200 aircraft and includes the A350-1000 aircraft.Powered by the latest generation Rolls-Royce Trent 7000 engines, the A330neo is designed to fly up to 8,100 nautical miles / 15,000 kilometers non-stop and reduces fuel burn, CO2 emissions and operating cost by 25% compared to previous generation competitor aircraft. The A350 is the world's most m...