If you see a green light on the left and a red on the right
This requires knowledge of two areas, firstly you must remember what colour navigation light is on each wing:
PORT = RED visible from dead ahead to 110 degrees to PORT
STARBOARD = GREEN visible from dead ahead to 110 degrees to STARBOARD
If at night the green light appears to be on the left and red on the right then the aircraft is coming towards you.
Secondly you need to know that when two aircrafts flight paths are head on, both aircraft should turn right
In addition to these lights, airships also show a single fixed white nose light that is visible through 110 degrees from either side.
Wing lights are required for night flight. If one fails during a night flight then the plane must land as soon as reasonably possible.
