Sky Adventure is a vertical Shoot 'em Up released in 1989 by Alpha Denshi and published by SNK.
From the game's intro:
"We who had been exploring a wild jungle were attacked by a misterious troop which suddenly appeared. It was Blue Mist, an underground organization led by Colonel Claud, an evil Generalissimo."
Players can choose between four ships before each stage, each with it's own strengths and weaknesses. The ships are equipped with a primary, forward firing gun and a secondary gun with limited ammo. During the stages a blimp will fly through and deliver power ups, ammo for the secondary gun and sometimes an item which allows the player to change his ship with another one.
In every stage, Colonel Claud will appear at the mid point and attack the players in a flying ship. Defeating him nets a score bonus, but if the player is destroyed then he will retreat and the player will lose the bonus.