Aircraft Navigation Lights

To make sure that aircraft are visible in the air to other pilots, navigation lights in white, green and red are used to help determine whether a plane is coming towards you or going away from you or crossing from one side to the other in front of you. This can be quite deceptive especially if you are flying at night.

Similar lighting is used for shipping, the light on the left (or Port) side of the ship or aircraft wing being red and that on the right (or Starboard) side of the ship or aircraft wing being green.

Therefore if you see lights in front of you, green on the left of the object and red on the right, the object is coming towards you and you need to take evasive action by turning to the right. The lighting is also screened as set out in the figure so that the different colours are not all seen at the same time potentially confusing you. If the aircraft was crossing from left to right in front of you, you should therefore see only the green light initially followed by the white tail light as the aircraft passes by. 

Many aircraft also now have bright flashing strobe lights to alert you to the aircraft's position earlier.