Of the 631 Sabreliner jet aircraft produced between 1963 and 1981, military and government sales accounted for 191. The U.S. Air Force bought the lion's share, with 149 originally purchased under its Utility Trainer Program (UTX). Only four months after North American Aviation flew the first T-39 prototype in September 1958, the Air Force placed its first production order for 143 T-39As and six T-39Bs. Both aircraft types were powered by two Pratt&Whitney J60 jet engines, each rated at 3,000 pounds of thrust at sea level.

One of the most important modifications to the KC-135 fleet is an engine retrofit, which for the last 20 years has been swapping the aircraft's Pratt&Whitney TF33 and Pratt&Whitney J57 powerplants with more modern and quieter General Electric/SNECMA F108s. The engine is built around the same core as the civil CFM56, which powers the Boeing 737-300, -400 and -500 airliners.

Although it is no longer the prime contractor for KC-135 programmed depot maintenance (PDM), Birmingham, Ala.-based Pemco Aeroplex continues to play a major role in the program under a subcontract to Boeing. As Boeing's huge San Antonio facility books more government work, particularly on the C-17 transport and the KC-10 tanker/transport, more KC-135 PDM is likely to be sent to Pemco.