Upgrading the remaining KC-135Es into KC-135Rs is no longer in consideration; this would have cost approximately US$3 billion, $24 million per aircraft. According to USAF data, the KC-135 fleet had a total operation and support cost in fiscal year 2001 of about $2.2 billion (~$ in ). The older E model aircraft averaged total costs of about $4.6 million per aircraft, while the R models averaged about $3.7 million per aircraft. Those costs include personnel, fuel, maintenance, modifications, and spare parts.
Upgrading the remaining KC-135Es into KC-135Rs is no longer in consideration; this would have cost approximately US$3 billion, $24 million per aircr:aft. According to USAF data, the KC-135 fleet had a total operation and support cost in fiscal year 2001 of about $2.2 billion (~$ in ). The older E model aircraft averaged total costs of about $4.6 million per aircraft, while the R models averaged about $3.7 million per aircraft. Those costs include personnel, fuel, maintenance, modifications, and spare parts.