As the 707-100 was being introduced and the long-range 707-300 was being planned, Boeing also decided to develop a 707 derivative with increased performance for short-to-medium range routes, allowing the plane to operate from shorter runways.
Initially the plane was identified as the 707-020, was later changed to 717-020 and, with input from launch customer United Airlines, was eventually designated the 720.
Outwardly the model 720 resembled the 707, but it was a very different airplane.
It had a much lighter structure and was 9 feet (2.74 meters) shorter than the 707-100. It also had an increased wing sweep on the leading edge between the fuselage and inboard engines as well as full-span Krueger leading edge flaps.
The 720 carried less fuel than the 707-100. Combined with its lighter structure, this gave the plane a lower gross weight, increased takeoff performance and a higher top speed.
The 720 went into service on July 5, 1960 with United Airlines. Boeing built 65 model 720s.
The only variant of the 720 was the 720B which first flew on October 6, 1960.
The main difference on the 720B was the installation of Pratt and Whitney JT3D Turbofan engines that increased the takeoff and climb performance as well as cruise speed of the plane.
Boeing built a total of 89 720Bs.
The 720 proved to be an economical plane to operate and was a favorite of pilots, passengers and operators alike.
The rapid pace of technology soon caught up with it as the more capable 727 replaced the 720 as the leader in the medium-range, high-performance market.
||130 feet 10 inches (39.9 m)
||135 feet 9 inches (41.4 m)
||41 feet 6.5 inches (12.7 m)
||601 mph (967 km/h)
||622 mph (1,001 km/h)
||12,500 pounds thrust P&W JT3C-7
||18,000 pounds thrust P&W JT3D-1