The Mitsubishi AAM-4 is a medium-range active radar homing air-to-air missile. It is a modern beyond-visual-range missile developed in Japan and intended to replace the semi-active radar homing AIM-7 Sparrow missile in service. It has been operational since 1999. The main contractor is Mitsubishi Electric. The AAM-4 had a development cost of 36.2 billion yen. The 2010 AAM-4B was the world's first air-to-air missile with an AESA radar seeker, though the missile's fins are too large to fit in the internal weapons bay of the F-35 Lightning II.