Boeing engine started in 1943 and Boeing's gas turbines were designated models 502 (T50), 520 (T60), 540, 551 and 553. Boeing built 2,461 engines before production ceased in April 1968. Many applications of the Boeing gas turbine engines were considered to be firsts, including the first turbine-powered helicopter and boat. Vertol Aircraft Corporation was acquired by Boeing in 1960, and was reorganized as Boeing's Vertol division. The twin-rotor CH-47 Chinook, produced by Vertol, took its first flight in 1961. This heavy-lift helicopter remains a work-horse vehicle to the present day. In 1964, Vertol also began production of the CH-46 Sea Knight.
Boeing Chinook (UK variants) such as the AgustaWestland Merlin HC.3 of the Royal Navy's Commando Helicopter Force and the RAF's Westland Puma HC.2, based at RNAS Yeovilton and RAF Benson. The RAF has a total of 60 active Chinooks in inventory as of 2015. In 2018 the UK issued a request to the United States to purchase 16 additional aircraft. The Chinook is expected to remain in RAF service until the 2040s. In March 1967 an order was placed for fifteen Chinook HC Mk1s, standing for "Helicopter, Cargo Mark 1", for the Royal Air Force to replace the Bristol Belvedere. This original MK1 variant