Boeing is looking at offering derivatives of the 737 MAX to replace NATO militaries’ fleets of aging and thirsty Boeing 707s, according to a report by Aviation Week. The Boeing 707 was the starting airframe for 140 special observation aircraft still in use around the world (including the E-6, E-3, E-8, RC-135, OC-135, and WC-135). The most produced military variant of the 707, the KC-135 Stratotanker, is being replaced by the Boeing KC-46A, which is derived from the Boeing 767 platform. Many of the Boeing 707 variants entered service in early 1960s.
Source: avwebBoeing Eyes Defense Market for 737