Air Fortress was developed by HAL Laboratory for the NES and, after being released in Japan in 1987, was released in North America in 1989. Prior to its North American release, it is believed that a small number of copies of the game were shipped to the USA in 1987 as a test run for the system, but the exact number of games pre-released is unconfirmed.
Air Fortress follows a fairly common alien invasion storyline: a planet develops space travel technology; ships are sent out to eagerly explore the galaxy; a deadly force is discovered heading towards their planet; the planet deploys its fleet in defense, but the ships are all defeated; in a final gambit, a single warrior is sent out to make a last stand against the encroaching threat.
In this game, the deadly force approaching are "Air Fortresses", which are intent on consuming all the resources and living creatures in their path, like locusts. The player controls the planet's final defense - Hal Bailman. This lonely space fighter is outfitted with a shielded spacesuit, powerful weapons, and small lightship adn tasked to infiltrate the Fortresses one by one and destroy them from within.
Each Air Fortress has two levels: an Air Base and the Fortress itself.
As Hal approaches to the Air Fortress, he has to battle through a number of enemies defending it, as well as dodge space debris. The gameplay for this part of each level is that of a side-scrolling shooter. Energy and weapon upgrades can be collected during this phase to use inside the Air Fortress. To move onto the next part of the level, the player must successfully reach the Air Lock.
The player has 3 chances to reach the Air Lock, and a single collision or hit will destroy Hal's ship and lose a life. Reaching the air lock is made a bit easier by a chance in the programming between in the Japanese release and the North American one, though: in the original version, each time Hal's lightship is destroyed, the player must restart the level, but in the subsequent North American release, the player will automatically respawn from the same point at which his ship was destroyed, provided he has extra lives.
Once the Air Lock is reached, the gameplay changes. Inside the Fortress, "Air Fortress" becomes an action-adventure game.
The player is able to control where Hal goes and explore the maze-like environment. As the levels progress, navigating the internal mazes of the Fortresses becomes on of the major challenges in defeating each level. As the player struggles through the maze, they must also deal with enemy robots and security devices before, ultimately, finding and destroying the central core of the Fortress. Once this is complete, Hal must race back to his ship to escape the Fortress. The player has only a very limited window of time to find the exit before the Fortress explodes, and this is made even more difficult by the fact that the exit is never the same as the entry point through which the player first entered the maze.
Overall, it is the combination of various types of gameplay, increasingly difficult enemies, complicated mazes and small windows for escape make Air Fortress a challenging game.