turbofan engines in place of the original models’ Lycoming units. On 10 April 1982, the CL-601 performed its maiden flight. According to Flight International, the decision to adopt the CF34 engine for the new model was responsible for generating a substantial boom in Challenger sales. According to Flight International, the slow initial sales of the Challenger heavily contributed to the near-bankruptcy of Canadair, which was only avoided by the purchase of the company by Bombardier in 1986. Bombardier elected not only to continue production of the type, but also to finance the development of new models and derivatives. This choice was aided by Canadair's design decision to enable the Challenger to be readily stretched from the onset. As of October 2018, the best-selling variant of the Challenger series has been the CL-604, which was launched in 1995. The 500th aircraft was rolled out in May 2000. The 1000th, a 650, was delivered to NetJets in December 2015. According to Flight International, the Challenger 600 has been a foothold in the market for Bombardier, allowing them to more easily develop further business jets, such as the Bombardier Global Express; another direct derivative of the Challenger series has been the Bombardier CRJ100 series, a larger regional airliner. The publication also commented that the Challenger family "appears to have a solid future", observing a production rate of two aircraft per month throughout 2018. Design The Challenger is a twin-engined business jet, described by Flight International as being a "miniaturised twinjet airliner in every respect". While the Challenger is generally similar in configuration to previous aircraft of its type, some of its features stand out; for example, a widened fuselage allows a "walk-about cabin". The Challenger was also one of the first business jets to be designed with a supercritical wing. The wing was referred to by Canadair as being one of the aircraft's most advanced features. It is also capable of performing short takeoffs while maintaining the speed and comfort levels normally associated with larger jetliners. The Challenger's wing has been referred to as being a modified NACA symmetrical aerofoil. Akin to other supercritical wings, it features a rounded leading edge, an inverted camber, a blunt trailing edge and scalloping of the underside. The twin-spar wing box structure spans the entire length of the wing and is compartmentalised to form five internal fuel tanks; these tanks can accommodate up to 14,661 lb of