Similar to Proto1, Airball (Proto2) for the NES is an early development version with little documented information. It represents a stage in the game's development process, likely indicating further refinements or adjustments to gameplay mechanics, graphics, or overall structure from the earlier prototype.  The developer behind it is uncertain. Examining differences between Proto1 and Proto2 may reveal iterative changes made during design.

Airball (Proto2)

Air Fortress (Japan) (Proto) (1986-10-20)