May 26,2008: The U.S. Air Force is retiring its oldest KC-135 aerial refueling aircraft. The recent retirement of this KC-135E, after 48 years service, leaves only one KC-135E still in service. But it will be retired soon, leaving only the KC-135R to serve for another 10-15 years (until the KC-45 replaces them).

The 157 KC-135Es were originally KC-135As that had their engines replaced with more powerful ones taken from retired commercial Boeing 707s (the commercial version of the KC-135). These aircraft were used by reserve units. Later, 500 more recent KC-135s had new engines installed, to produce the KC-135R. The replacement engines enabled the tankers to carry more fuel and stay in the air longer.

Retired KC-135s are placed in storage at the air force "bone yard" in Arizona. There, the aircraft stand ready for activation in a national emergency or, as is more likely, being picked apart for spare parts, and eventually being chopped up for scrap metal.