Source: Wikipedia, "US-AAF Mustang", available under the CC-BY-SA License.
US AAF Mustang is a horizontally scrolling shoot 'em up arcade game originally developed by NMK, and published by UPL in 1990. It was ported a year later to the Sega Mega Drive by Taito while being renamed Fire Mustang. NMK Co. Ltd. also developed the Sega Mega Drive version.
The game is a very standard horizontal scrolling shoot em' up with only one type of available weapon and a bomb weapon. Players took on a fictional campaign in a World War II setting as a USAAF fighter pilot in a titular P-51 Mustang against the Nazi Luftwaffe and the Imperial Japanese Navy Air Service.
Players were sent around stages in Europe and Asia against either of the two featured Axis powers. Every level was filled with a wide variety of different fighter craft and ground forces that all preceded the end-level boss (generally a large aircraft).
Players had a typical vulcan weapon that could be upgraded three times in order for the shot pattern to widen. Players also had an unlimited amount of ground force bombs that would increase in firing speed with the vulcan. The player's bomb weapon was a weapon called "The Forcer" that fired a large fireball straight forward.
While the arcade original featured a second player to join in, the 2 player addition was removed from the Mega Drive port
Despite the game's setting, certain liberties are taken from real life as well as anachronisms.
The first mission takes place in 1940, near Spain, but Spain was a neutral country and never joined the Axis and the United States had not joined World War II until December 1941.
P-51 Mustangs were not available until late 1943 and neither were the Dornier Do 335 fighter planes first encountered in the first level (flying in a rectangular formation) which was not issued or used by the Luftwaffe until mid-1944.
The most obvious, but more excusable, inaccuracies include the Vulcan and Forcer weapons as well as the enemy ground force's use of homing missiles; most of which were used for the sake of arcade game challenge and presentation.