Self-Guided Missle

Game:

A self-guided missile that uses the sound of the target plane's engine to guide itself. It can also be used against ground targets, but cannot self-guide in this case. Unlike modern guided missiles, it is not a smart weapon - it is not locked on the original target and can switch target in mid-air if another plane intersects its path. If you launch the missile too far away from the target, then it will not lock on and hit the target.

In real life, the missile was called the Ruhrstahl X-4.

Wikipedia page here