The REIL (Runway End Identifier Lights) system consists of two synchronized flashing lights, unidirectional or omni-directional, one on each corner of the runway-landing threshold at an angle of 10 to 15 degrees. The unidirectional lights face the approach area.
REIL is effective for identification of a runway surrounded by a preponderance of other lighting; identification of a runway which lacks contrast with surrounding terrain; and identification of a runway during reduced visibility
The REIL provides three intensity settings, and has an approximate range of three miles during daylight and twenty miles at night.
The REIL can be controlled by the air traffic control tower, remotely by the pilot, by sending the current through the runway edge lights, or manually in the control cabinet.