A short-to-medium-range narrowbody jetliner built by Boeing from 1958 through 1967 as a shortened version of the 707.
The Boeing 720 was a four-engine narrowbody jetliner produced by boeing between 1958 and 1967; essentially a cut-down, lightened version of the boeing-707 fitted with a more efficient wing, it was designed for shorter flights from smaller airports than its larger parent. The first 720 took to the air in November 1959, and the aircraft entered service with United Airlines in July of the following year. As almost all of the 720's systems remained the same as those on the 707, its development costs were nearly zero, and Boeing, therefore, was able to make a tidy profit from the 720 despite its fairly small production run of only 154 aircraft.
The 720 is the only Boeing-designed jetliner (other than the boeing-sst, which never entered production) ever to receive a designation not conforming to the company's famous "7x7" naming scheme; it was originally to be called the 707-020, but this was changed at United Airlines' request (United had publically committed to douglas's rival dc-8, and didn't want it to seem like they were going with the 707 instead).
Two main variants of the 720 were produced:
- The original 720, which used Pratt & Whitney JT3C turbojet engines; 65 were built from 1958 through 1963.
- The 720B (produced from 1960 through 1967) differed from the original 720 primarily in using the more powerful and less fuel-thirsty JT3D engine, a turbofan (which made the 720B more fuel-efficient and gave it a higher top speed), and, indeed, ten 720Bs were straight reengines of preexisting 720s. The 89 720Bs that were built as such (rather than being reengined 720s) had slightly larger fuel tanks and a modified tail in addition to the new engines, but were still very similar to the original 720.
Production of the 720 ended in 1967, having been succeeded by the boeing-727, which entered service in 1964. The major U.S. airlines replaced their 720s with 727s during the 1970s, although the 720 hung on in commercial service elsewhere until 1989; the last 720 in use by anyone for anything (used by Pratt & Whitney Canada as an engine testbed) was retired in September 2010, and made the very last flight ever by a 720 (to the museum that would be its final home) on 9 May 2012.
See Wikipedia for more information about the 720.