In continuing development of their first swept-wing jet, Mikoyan-Gurevich improved on the MiG’s design continuously from the onset. Of no little importance in this work was intelligence coming to Russia from the West on the North American F-86 development. Incorporating a fuselage that was three feet longer than that of the MiG-15, a new MiG-15bis I-330 fighter design was introduced. Shortly thereafter designated the production designation of MiG-17, the improved aircraft featured a number of refinements that included a sweep of forty-five degrees (instead of thirty-five), a new, thinner wing-section (for improved speed), and enlarged air-brake panels. Also incorporated was an up-rated engine (the Klimov VK-1F, rated at about 7,450 pounds of thrust with afterburner) that increased maximum speed to about 711 mph (Mach 0.98). First flight of the MiG-17 occurred in January of 1950. Nominal ceiling of the new aircraft was about 57,000 feet. Production of the MiG-17 began in late 1951, and the first operational MiG-17s appeared in 1952. There were not enough of them to be introduced during the Korean conflict, but 5 subsequent models of the MiG-17 design saw extensive service in the Vietnam War of 1965-1975. Weighing about 13,400 pounds (maximum take-off weight), and armed with two 23 mm cannons and one 37 mm cannon, the MiG-17 packed a formidable punch in its air-to-air combat role.