As of January 2011, Delta operates a fleet of more than 700 aircraft manufactured by Airbus, Boeing, and McDonnell Douglas. The carrier operates the largest fleets of Boeing 757, Boeing 767and Airbus A330aircraft of any US airline. Delta operates the largest fleet of MD88 and MD90 aircraft in the world, and was one of the last major airlines to operate the original Boeing 737–200models, which were retired in 2006. Prior to its 2008 merger with Northwest Airlines, Delta’s fleet was made up of Boeing and McDonnell Douglas aircraft; Northwest’s Airbus aircraft joined the fleet after the merger. As of April 14, 2011, all of Delta’s mainline aircraft have been painted in the carrier’s latest livery.
As of March 31, 2012, the average age of the Delta fleet is 15.8 years, excluding grounded aircraft and those operated by contract carriers. The oldest aircraft in the fleet are the McDonnell Douglas DC-9-50s with an average age of 34 years and the McDonnell Douglas MD-88s with an average age of 21.7 years. To replace the DC-9s, MD-88s, and older A320 and 757-200 aircraft in their fleet, Delta began discussing narrow body replacement plans with manufacturers such as Airbus, Boeing and Bombardier in early 2011.
On August 22, 2011, it was announced that Delta has placed an order for 100 Boeing 737-900ER aircraftand deferred an order of 100 small narrow-body jets until 2012.
On May 22, 2012, Delta announced an agreement with Southwest Airlines to lease the entire 88-plane Boeing 717fleet that it inherited from its acquisition of Air Tran Airways. as a replacement for the remaining DC-9s and replacement for the small 50 seat regional aircraft. Deliveries should begin in mid-2013 replacing over 250 CRJs 100/200 aircraft.