The 707 was designated the 720 when it was modified for short- to medium-range routes and for use on shorter runways. Engineers reduced the fuselage length by 9 feet (2.7 meters), changed the leading edge flaps and later installed turbofan engines. Boeing built 154 720s between 1959 and 1967. Its short- to medium-range role was later filled by 727s and 737s.