took place in early September. The prototype was marked with the new PAF designation JF-17. By March 2004, CAC had made around 20 test flights of the first prototype. On 7 April 2004, PAF test pilots Rashid Habib and Mohammad Ehsan ul-Haq flew PT-01 for the first time. The maiden flight of the third prototype, PT-03, took place on 9 April 2004. In March 2004, Pakistan was planning to induct around 200 aircraft. Following the third prototype, several design improvements were developed and incorporated into further aircraft. Because of excessive smoke emissions by the RD-93 engine, the air intakes were widened. Reported control problems found in testing resulted in alterations to the wing leading edge root extensions (LERX). The vertical tail fin was enlarged to house an expanded electronic warfare equipment bay in the tip. The redesigned aircraft had a slightly increased maximum take-off weight and incorporated an increased quantity of Chinese-sourced avionics; however PAF had selected Western avionics for their aircraft, postponing PAF deliveries from late 2005 until 2007. Pakistan evaluated British, French, and Italian avionics suites, the winner of which was expected to be finalised in 2006. PT-04, the fourth prototype and the first to incorporate the design changes, was rolled out in April 2006 and made its first flight on 28 April 2006. The modified air intakes replaced conventional intake rampswhose function is to divert turbulent boundary layer airflow away from the inlet and prevent it entering the enginewith a diverterless supersonic inlet (DSI) design. The DSI uses a combination of forward-swept inlet cowls and a three-dimensional compression surface to divert the boundary layer airflow at high sub-sonic and supersonic speeds. According to Lockheed Martin, the DSI design prevents most of the boundary layer air from entering the engine at speeds up to two times the speed of sound, reduces weight by removing the need for complex mechanical intake mechanisms, and is stealthier than a conventional intake. In 1999, developmental work on the DSI with the aim of improving aircraft performance commenced. The JF-17 design was finalised in 2001. Multiple models underwent wind tunnel tests; it was found that the DSI reduced weight, cost, and complexity while improving performance. For the avionics and weapons qualification phase of the flight testing, PT-04 was fitted with a fourth-generation avionics suite that incorporates sensor fusion, an electronic warfare suite, enhanced man-machine interface, Digital Electronic Engine Control (DEEC) for the RD-93