Military Aircraft: Considerations in Reviewing the Air Force Proposal to Lease Aerial Refueling Aircraft Page: 3 of 15
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similar to the Boeing-707 airliner. Because of their large numbers, the
KC-135s are the mainstay of the refueling fleet, and successfully carrying
out the refueling mission depends on the continued performance of the
KC-135s. Thus, recapitalizing this fleet of KC-135s will be crucial to
maintaining aerial refueling capability, and it will be a very expensive
There are two basic versions of the KC-135 aircraft, designated the
KC-135E and KC-135R. The R model aircraft have been re-fitted with
modern engines and other upgrades that give them an advantage over the
E models. The E-model aircraft on average are about 2 years older than
the R models, and the R models provide more than 20 percent greater
refueling capacity per aircraft. The E models are located in the Air
National Guard and Air Force Reserve. Active forces have only R models.
Over half the KC-135 fleet is located in the reserve components.
The rest of the DOD refueling fleet consists of Air Force HC- and MC-130
aircraft used by special operations forces, Marine Corps KC-130 aircraft,
and Navy F-18 and S-3 aircraft. However, the bulk of refueling for Marine
and Navy aircraft comes from the Air Force KC-10s and KC-135s. These
aircraft are capable of refueling Air Force and Navy/Marine aircraft, as
well as some allied aircraft, although there are differences in the way the
KC-10s and KC-135s are equipped to do this.
Condition of Aerial The KC-10 aircraft are relatively young, averaging about 20 years in age.
Consequently, much of the focus on modernization of the tanker fleet is
Refueling Fleet centered on the KC-135s, which were built in the 1950s and 1960s, and now
average about 43 years in age.
While the KC-135 fleet averages more than 40 years in age, the aircraft
have relatively low levels of flying hours. The Air Force projects that E and
R models have lifetime flying hours limits of 36,000 and 39,000 hours,
respectively. According to the Air Force, only a few KC-135s would reach
these limits before 2040, but at that time some of the aircraft would be
about 80 years old. Flying hours for the KC-135s averaged about 300 hours
per year between 1995 and September 2001. Since then, utilization is
averaging about 435 hours per year.
According to Air Force data, the KC-135 fleet had a total operation and
support cost in fiscal year 2001 of about $2.2 billion. The older E model
aircraft averaged total costs of about $4.6 million per aircraft, while the
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United States. General Accounting Office. Military Aircraft: Considerations in Reviewing the Air Force Proposal to Lease Aerial Refueling Aircraft, text, July 23, 2003; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc292631/m1/3/: accessed February 18, 2020), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.