Originally Posted by
BKS Air Transport
Having mentioned it, could someone tell me why the 720B was regarded as being sufficiently different from the 707 so as to have its own designation?
Despite the superficial resemblance between the 707-120 and the 707-020, there were sufficient differences between the two to warrant a separate Type Certificate for the latter and a change in designation to the 720 (suggested by launch customer, United).