Air Duel is a vertically scrolling shoot 'em up arcade game released by Irem in 1990. You can select from a fighter jet or helicopter, shoot enemies in the air and ground, collect power-ups, and defeat bosses to advance levels.
The game differs from most others in the genre in that you can change the aircraft you use at the start of each new level. The fighter always shoots straight forward, though power ups multiply the width and power of its shots. The helicopter can spray shots diagonally, but always fires a narrow beam. Power ups give it more rapid fire.
There are no different kinds of weapons, only different levels of power, and losing a life resets your power to the level you start with. "Air Duel" is a challenging game, and later levels become nearly unplayable if a single life is lost.
Both the fighter and the helicopter also start with three bombs which wipe out everything in their path, including enemy shots. Additional bombs can be picked up during the course of the game.
While far less successful than the classic Irem shooter "R-type," "Air Duel" provides an early example of the post-apocalyptic style that can be seen in other Irem games, such as "Undercover Cops" and "In the Hunt." Some of the Irem staff left to form Nazca, and stylistic similarities appear throughout the "Metal Slug" series.
A sequel to "Air Duel," Air Assault, was released in 1993.