standards. Japan selected the fighter to replace the F-4EJ and supplement the F-15J, its main air superiority fighter. The program involved technology transfer from the U.S. to Japan and vice versa. Responsibility for cost sharing was split 60% by Japan and 40% by the U.S. Lockheed Martin would manufacture all the aft fuselages and wing leading-edge flaps and eight of the ten left-hand wingboxes. The F-2 program was controversial, because the unit cost, which includes development costs, is roughly four times that of a Block 50/52 F-16, which does not include development costs. Inclusion of development costs distorts the incremental unit cost (this happens with most modern military aircraft), though even at the planned procurement levels, the price per aircraft was somewhat high. The initial plan of 141 F-2s would have reduced the unit cost by up to (€7.5 million) per unit, not including reduced cost from mass production. As of 2008, 94 aircraft were planned. The F-2's maiden flight was on 7 October 1995. Later that year, the Japanese government approved an order for 141 (but that was soon cut to 130), to enter service by 1999; structural problems resulted in service entry being delayed until 2000. Because of issues with cost-efficiency, orders for the aircraft were curtailed to 98 (including four prototypes) in 2004. Flight testing of the four prototypes were conducted by the Japan Defense Agency at Gifu Air Field. The last of 94 production aircraft ordered under contract was delivered to the Defense Ministry on 27 September 2011. During the roll-out ceremony of the last production F-2 fighter jet, Mitsubishi Heavy Industries confirmed that production of the F-2 would end and no more F-2 fighters will be produced by the manufacturer. there are 61 single-seaters flying, and 21 two-seat trainers. Design General Electric, Kawasaki, Honeywell, Raytheon, NEC, Hazeltine, and Kokusai Electric were among the primary component sub-contractors. Lockheed Martin supplied the aft fuselage, leading-edge slats, stores management system, a large percentage of wingboxes (as part of two-way technology transfer agreements), and other components. Kawasaki built the midsection of the fuselage, as well as the doors to the main wheel and the engine, while the forward fuselage and wings were built by Mitsubishi. Some of the avionics were supplied by Lockheed Martin, and the digital fly-by-wire system was jointly developed by Japan Aviation Electric and Honeywell (formerly Allied Signal). Contractors for communication systems and IFF interrogators included: