Originally an air-to-air missile with semi-active radar homing (SARH), the early versions of the AIM-7 Sparrow were not considered very useful in the Vietnam War. The rules of engagement often required visual identification, so the Sparrow's beyond visual range capability was often not usable. In addition, the SARH transmitter had to be on the launching aircraft, so the launcher had to keep flying at the target, possibly getting in range of its weapons, and certainly being on a course predictable by other enemy aircraft.
Later models had increased range, better resistance to electronic warfare, and had a final infrared plus radar seeker that let the launching aircraft maneuver once the Sparrow was close to the target. Nevertheless, the AIM-7 has been replaced by the AIM-120 AMRAAM for air-to-air missiles.