Fly with the 1st, 2nd, and 3rd Element squadrons as you defend country and, eventually, Earth itself from attack. Pilot aircraft that span sixty years of aviation including WWII prop planes, Korean War jets, rare prototypes, and even aircraft from previous Konami games like the Vic Viper and TwinBee.

Between missions you can explore the base and talk to wingmates, buy new aircraft and special weapons, modify or repaint existing aircraft, and get mission briefings. Missions can have varied objectives, but any enemy crafts shot down will reward money used to buy, modify, and repair aircraft. While Ken Thomas is the main character of the game, other pilots can be used in missions as the game progresses, and using them can open up bonus missions as well as alter the story. The player can only play as Delta Squadron pilots, but the story is told from the perspective of both E.D.A.F.'s Delta Squadron and their O.C.C. Ace counterparts. Medals are awarded to each pilot as they reach milestones, such as number of enemy aces shot down or number of aircraft purchased.

The game plot occurs in an unspecified time in the future, featuring sci-fi weapons, planes and environments. When OCC (Orbital Citizen Community), a space colony set on Earth's orbit, rebels and launches an invasion of Earth, EDAF (Earth Defense Allied Forces) launches a defensive campaign. EDAF is overwhelmed by the OCC's superior weapons and numbers early in the war, losing a majority of its conventional forces and is forced to enlist any militia forces to help, including the Delta Squadron, an ill-famed aerial strike group known as a "dumping ground" for disgraced or misfit pilots. Despite their differences, Delta Squadron's efforts allow the EDAF to turn the tide and liberate portions of Earth occupied by the OCC, earning them the attention and rivalry of the OCC's elite experimental squadron. As the tide starts to turn and as the Earth forces advance, they find out that OCC is not the major threat - an organization from Mars is planning to destroy Earth with the help of the orbital colony.