Boeing C-137 Stratoliner

The Boeing C-137 Stratoliner is a retired VIP transport aircraft derived from the Boeing 707 jet airliner and used by the United States Air Force; other nations also bought new and used 707s for military service, mainly as VIP or tanker transports. It should not be confused with the similar C-135 Stratolifter, since the two share a common ancestor but have different fuselages among other structural differences. Air Force procurement of the 707 was very limited: three Model 707-153s were designated VC-137A, delivered in 1959 with Pratt & Whitney J57 turbojets and later re-engined with TF33 turbofans as the VC-137B. The VC-137C was the Air Force One presidential transport, two Model 707-320B Intercontinentals with specialised interiors and advanced communications, and two further C-137C aircraft without presidential modifications were later added. The C-18 designation covers later variants based on the 707-320B and C.