Sonic Wings Special is a vertical-scrolling shoot 'em up that combines the features in Sonic Wings, Sonic Wings 2, Sonic Wings 3.
There are 7 teams, 14 pilots, and 26 fighters in this game, with each team consist of 2 members, and a choice of 2 fighters per pilot, except the secret team, which has 1 fighter per pilot.
Once a player is chosen a team, the other player can only choose pilot and fighter of the respective team.
A pilot's secret fighter is unlocked by completing the game with the chosen pilot.
The NATO and Secret teams are unlocked by unlocking all secret fighters in USA, Japan, Russia, Sweden, P.K.F. teams.
There are 17 stages in this game, but only 9 are playable at a time. After completing stage 1, 3 stages are randomly chosen out of 5. The game includes a branching system that allows player to choose 1 of 2 branches after completing stages 5, 7, or 8.
If secret fighter is chosen, alternate version of the stages appear instead.
Source: Wikipedia, "Sonic Wings Special", available under the CC-BY-SA License.