Yeah, I always thought it was Alien Storm, but the "smart bomb" I mentioned is pretty particular. I'm certain they don't have that in Alien Storm.
Are you sure? Each player had a different attack, I'm sure one of them was a ship flying over, on the arcade ver at least.
From Gamefaqs:
Karen's Special Attack: Missile
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A large missile drops down from the sky, followed by a splitting explosion that
clears the enemies on-screen.
Scooter's Special Attack: Full-body Explosion
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Scooter's body completely blows up and shards of metal fly in different
directions, wiping out on-screen enemies. The head is left behind, and a
replacement body runs on-screen, picks it up and places it back on the
shoulders.
Garth's Special Attack: Airstrike
---------------------------------
Garth calls on an air vessel that flies overhead and shoots down to take out
all on-screen enemies.