The first prototype, powered by two imported Nenes, made its maiden flight on 8 July 1948, with Vladimir Kokkinaki at the controls. Testing was successful, with the Il-28 demonstrating good handling and reaching a speed of 833 km/h (518 mph). It was followed on 30 December 1948 by the second prototype, with Soviet built RD-45 engines replacing the Nenes. After the completion of state tests in early 1949 the aircraft was ordered into large scale production on 14 May 1949, with the Klimov VK-1, an improved version of the RD-45 to be used in order to improve the aircraft's performance. The first pre-production aircraft with VK-1 engines flew on 8 August 1949, and featured reshaped engine nacelles to reduce drag, while the radome for the navigation radar was moved from the rear fuselage to just aft of the nosewheel.