Falcon 4.0: Allied Force (F4AF) is an F-16 based combat flight simulator released by Lead Pursuit on 28 June 2005. The game is based around a realistic simulation of the Block 50/52 F-16 Fighting Falcon in a series of missions in the Balkans. The game engine is based on the source code of the original 1998 Falcon 4.0 from MicroProse, and consists largely of a collection of improvements from the official patches and extensive Falcon modding community. Allied Force also introduced several major new features and significant improvements in realism and stability.