ExocetExocet

In Exocet, you first pilot a spacecraft over the surface, shooting the defense towers in your path. The larger towers are too large to fly around, and they must be hit at the point where they fire. When you have traveled a particular distance, you will find an opening to the underground passage. There you continue to destroy the various things flying around.

Also sold under the name "Cruise Missile" by Froggo Games.