Boeing 720B

The Boeing 720B is a short‑range, narrow‑body jet developed by Boeing in the late 1950s as a derivative of the 707. First flown on July 15, 1959, the 720 entered commercial service the following year, providing airlines with a lower‑weight, lower‑cost alternative for medium‑distance routes that did not require the full payload of a 707. Boeing equipped the 720B with upgraded Pratt & Whitney JT3C turbo‑jets and later the more efficient JT3D turbofans, boosting thrust to 13,500 pounds and improving fuel consumption by roughly 15 percent. The aircraft featured a lighter airframe, a simplified wing design without the 707’s leading‑edge slats, and a more compact horizontal stabilizer, which together reduced operating costs while maintaining a cruising speed of Mach 0.78 and a range of about 2,500 nautical miles. Over 150 units were built, serving carriers such as Pan Am, Eastern, and TWA, and later many were converted to freighters or used as government transport. The 720B demonstrated the viability of derivative designs, accelerated the spread of jet propulsion in worldwide airlines, and paved the way for the highly successful 727 and early wide‑body programs.

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