720Bs were built; production ended in 1967. As a derivative, the 720 had low development costs, allowing profitability despite relatively few sales.

Compared to the 707-120, it has a length reduced by 8.33 feet (2.54 m), a modified wing and a lightened airframe for a lower maximum takeoff weight. Originally designed to be powered by four Pratt & Whitney JT3C turbojets, the initial 720 could cover a range with 131 passengers in two classes.