Delta Air Lines cut its fuel consumption by 1.8% from 2009 to 2010, which represents 56 million gallons of jet fuel.
The Atlanta-based carrier cited those statistics in its recently-released social responsibility report.
Delta attributes most of the reduction to its decision to "exit the dedicated freighter business". In 2009 Delta retired 10 dedicated Boeing 747-200 freighters operated by Northwest, which merged with Delta in 2008. At the time Delta said it grounded the aircraft due to "age and inefficiency".
But the carrier stressed it has "also made additional fleet changes and implemented or expanded fuel projects to further improve its fuel efficiency".
Delta continued the installation of blended winglets across its fleet, installing them on 21 Boeing 737-800s, 15 757-200s, and 14 767-300ERs. The carrier also increased "the utilisation of single-engine taxi procedures" and improved "arrival sequencing software in Atlanta to take into account gate availability".
Delta also said it refitted its fleet of 777-200ERs with a performance improvement package. The carrier operates eight of these aircraft, according to a 5 May regulatory filing.
In addition, the airline said it increased "the number of routing options for international flights", expanded its engine wash programme to include more fleet types, adjusted "descent procedures for uncongested airports", and decreased "the amount of unplanned fuel boarded on the aircraft".
"As a result of these improvements and higher load factors, passenger-miles increased by 2.7 percent despite a 0.1 percent reduction in passenger aircraft fuel" said Delta.
The carrier also outlined changes in its fleet, explaining that it has been "aggressively reducing its capacity flown by regional partners, which use less fuel efficient regional jets and turboprops. Since 2009, Delta has retired 143 fifty-seat regional jets and turboprops and plans to remove an additional 140 of its least efficient aircraft by mid-2013."
Delta noted in the report that it had retired 27 DC-9 aircraft last year and plans to retire the aircraft type by the fourth quarter of 2012. In addition, the carrier is growing its fleet of MD-90s, which "offer 50 percent more capacity per gallon than the DC-9s they will replace".
Earlier this year Delta issued an RFP "to manufacturers for a number of new, fuel efficient narrow-body aircraft with delivery starting in 2013".