Military Aircraft:

Information on Air Force Aerial Refueling Tankers

GAO-03-938T: Published: Jun 24, 2003. Publicly Released: Jun 24, 2003.

Additional Materials:


Neal P. Curtin
(757) 552-8100


Office of Public Affairs
(202) 512-4800

Both the Congress and the Department of Defense are concerned about the age of the U.S. aerial refueling fleet and its potential impact on the military services' ability to meet operational requirements. Aerial refueling provides a key capability that is essential to the mobility of U.S. forces. At present, the Air Force is in the early stages of planning for modernizing its aging fleet. In this testimony, GAO was asked to present its initial observations on (1) the status of the KC-135 fleet, including its age, projected life limits, and mission capable rates (i.e., the percent of time on average that the aircraft are available to perform their assigned mission); and (2) Air Force aerial refueling requirements.

The Air Force fleet of KC-135 aircraft (which, at 543 aircraft, represents the bulk of U.S. refueling capability) is an average of about 42 years in age. The Air Force projects that the KC-135 aircraft have between 36,000 and 39,000 lifetime flying hours; according to the Air Force, only a few KC-135s are projected to reach these limits before 2040, although at that time some of the aircraft would be close to 80 years old. KC-135s are being flown an average of about 435 hours per year, on average, since September 2001. As the fleet has aged, the aircraft have become expensive to maintain, averaging about $4.6 million per year in total operations and support costs for the least capable aircraft. Those costs include personnel, fuel, maintenance, and spare parts. KC-135s in the active duty forces are generally meeting the 85 percent goal for mission capable rates; rates were lower for aircraft in the reserve forces, ranging from 70 to 78 percent. The Air Force Reserve and Air National Guard operate over half of the KC-135s. In a 1996 report, GAO pointed out that the aging fleet of KC-135s would eventually need replacement and that the Department of Defense needed to start planning for the recapitalization of the fleet. At that time, the Department responded to our report saying that the current fleet would meet requirements "for the foreseeable future" and planned to begin procurement of new tankers around fiscal year 2013. In 2000, the Air Force conducted a study called the Tanker Requirements Study-05, but it was never formally completed. Therefore, DOD does not have a current, validated study on which to base the size and composition of either the current fleet or a future aerial refueling force. There is no effort currently under way to update the Air Force study or to conduct an analysis of alternatives for tanker modernization. The Air Force indicated recently that it plans to conduct a new Tanker Requirements Study in the fiscal year 2004-2006 time frame.

Jan 19, 2017

Jan 10, 2017

Dec 8, 2016

Dec 7, 2016

Dec 5, 2016

Dec 1, 2016

Nov 30, 2016

Nov 28, 2016

Nov 21, 2016

Looking for more? Browse all our products here