The SM-2 incorporates a new autopilot giving it inertial guidance in all phases of flight except for the terminal intercept where semi-active radar homing is still used.

NATO pilots use the brevity code Fox One in radio communication to signal launch of a Semi-Active Radar Homing Missile such as the Sparrow.

When this proved to be beyond the state of the art, further development as a semi-active radar homing followed, but this produced a very large missile with a range similar to the much smaller AIM-7 Sparrow.

One flaw of semi-active radar homing is that the launch aircraft must illuminate the target with its radar during flight, meaning that it must fly towards the enemy and so expose itself to greater danger.