All being well, the very last flyable Boeing 720 is due to land for the final time today at CFB Trenton, a Canadian Forces base in Ontario, after a short flight from Saint-Hubert in Quebec. The aircraft will be inducted into the National Air Force Museum of Canada on indefinite loan from Pratt & Whitney Canada which has used it as a flying engine testbed since the 1980s.
The flight marks the final chapter in the history of the 720 which began with the type’s first flight on November 23, 1959 at Renton, Washington. Although the majority of the 720s have long since gone, this last survivor is one of a handful of the slightly younger Pratt & Whitney JT3D turbofan-powered 720B variants that soldiered on into the 1990s and 2000s as flying testbeds for a variety of engine, sensor and avionics companies.
Originally operated by American Airlines and later Middle East Airlines, the 720B’s wide speed range and 45,000-ft max ceiling capability made it a good candidate for a testbed covering everything from turboprops to small business jet turbofans. PWC eventually acquired four 720Bs, although only two were flown as testbeds with the other pair being bought for spare parts. The other testbed, scrapped in the late 2000s by Pratt & Whitney, was based in Plattsburgh, New York, and used for evaluating the PW6000 amongst other programs. Both 720Bs have been replaced by 747SPs.
The 720 was launched as a high performance, short-to-medium range derivative of the 707. Configured with a 9-ft shorter fuselage than its longer sister, and with a lighter structure, the leading edge of the wing was also modified with an inboard ‘glove’ to increase sweep and boost cruise speed by 14 mph. Initially launched as the 707-020, the model was later re-designated the 717-020 before becoming the 720 at the behest of William ‘Pat’ Patterson, the president of launch customer United Airlines.
Boeing built 65 baseline 720s and 89 720Bs before being superseded by the 727. Although small by today’s numbers, Boeing considered the 720 a major success. Also, as Jon Proctor notes in his excellent book on the model, the 720 led to market dominance in the medium-range market. Some 75% of the original 720 owners went on to buy 996 727s.
One 720B famously met a spectacular fiery end when it was deliberately crash-landed at Edwards AFB in a joint NASA/FAA controlled impact demo of an anti-misting kerosene fuel.