Guardian of Earth — Michael Dahl

During a routine test flight above the deserts of the Southwest, ace pilot HAL JORDAN has a too-close-for-comfort encounter with a UFO. His jet takes a nosedive, but before HAL bites the dust, a gigantic green hand appears, grabs the aircraft, and prevents the crash. The mysterious UFO reveals HAL'S alien rescuer who possesses an amazing green ring of untold power. What does HAL do when the alien offers him the ring, and announces that the human pilot is now the new GUARDIAN OF EARTH?