<hi style=afpcap>The C-135 series was initially produced as the KC-135 for the air refuelling role, although it was inevitable the Stratotanker would be developed for other purposes. Three KC-135As were modified to interim C-135A standard pending completion of the standard version. Fifteen C-135As were ordered in 1960 and 1961 followed by 30 C-135Bs in 1961 and 1962. The three modified aircraft were constructed with shorter fins than the production models, although these were retrofitted subsequently. The delivery of the 45 C-135A and B models enabled the interim aircraft to be converted to reconnaissance duties with Strategic Air Command as RC-135Ds. The three aircraft were converted yet again, this time becoming KC-135As with the installation of the refuelling boom and associated plumbing. However this was not the end of the story as all three received the new F108-CF-100 engines becoming KC-135Rs.</hi>
