 The 707 production line remained open for purpose-built military variants until 1991, with the last new-build 707 airframes built as E-3 and E-6 aircraft.Traces of the 707 are still found in the 737, which uses a modified version of the 707's fuselage, as well as the same external nose and cockpit configurations as those of the 707.These were also used on the previous 727, while the 757 also used the 707 fuselage cross-section.