The 707-220 was designed for hot and high operations with powerful Pratt & Whitney JT4A-3 turbojets, only five of these were produced, however only four were ultimately delivered with one being lost during a test flight. All were for Braniff International Airways and carried the model number 707-227. This version was made obsolete by the arrival of the turbofan-powered 707-120B.
The first commercial orders for the 707 came on October 13, 1955, when Pan Am committed to 20 707s and 25 Douglas DC-8s, a dramatic increase in passenger capacity over its existing fleet of propeller aircraft. The competition between the 707 and DC-8 was fierce. Several major airlines committed only to the DC-8, as Douglas Aircraft was a more established maker of passenger aircraft at the time. To stay competitive, Boeing made a late and costly decision to redesign and enlarge the 707's wing to help increase range and payload. The new version was numbered 707-320.