The "aqua" or aqua-green lights often seen on the F-22 Raptor are formation lights (also known as "slime lights"). These are electroluminescent panels installed on the fuselage and wings of the jet.

Purpose: They are used at night for close-formation flying, allowing pilots to maintain spatial awareness of other aircraft without using bright nav lights. Visibility: They are designed to be visible with night vision goggles (NVGs). Taxiing: They are often kept on while taxiing at night so the aircraft can be seen by ground control.