The Mitsubishi AAM-4 (Type 99 air-to-air missile, 99式空対空誘導弾 (99 Shiki Kūtaikū Yūdōdan)) is a medium-range active radar homing air-to-air missile, considered as 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 improved AAM-4B was the world's first air-to-air missile with an AESA radar seeker. The AAM-4B entered production in 2010 for service on the F-15J and F-2, but it is too large to be carried in the weapons bay of the F-35 Lightning II. So on 17 July 2014 Japan announced a collaboration with the United Kingdom to study the development of a new Joint New Air-to-Air Missile (JNAAM). MBDA UK is prime contractor on the Meteor missile which entered service on the Saab JAS 39 Gripen in 2016 and on the Eurofighter Typhoon and Dassault Rafale in 2018, and can fit in the internal weapons bay of the F-35. It has a unique variable-flow ramjet motor that according to MBDA gives the Meteor the largest no-escape zone of any air-to-air missile. The JNAAM will "[combine] the UK's missile-related technologies and Japanese seeker technologies", possibly with some adjustments to help the missile fit better in the F-35 weapons bay.