The external lights on aircraft fall into two categories. The first is navigation lights that are always illuminated while the aircraft is in operation. A second type includes takeoff and landing lights that are used to improve visibility when the plane is close to or on the ground.
Navigation lights: All aircraft are equipped with a steady light near the leading edge of each wingtip. When facing forward from the perspective of the pilot, the light on the right wingtip is green while that on the left wing is red. The different colors make it possible for an outside observer, such as the pilot of another aircraft, to determine which direction the plane is flying. These navigation lights are most useful at night when it is more difficult to tell the direction the plane is going without them.
Navigation/Position lights: In addition to the red and green lights, most planes are also fitted with other steady white navigation lights in various locations. Large airliners, in particular, will often have such lighting on the trailing edge of each wingtip. These lights are also sometimes placed along the trailing edges of the horizontal tail. Another popular location is at the very aft end of the fuselage or at the top of the vertical tail. One of these latter lights placed along the aircraft centerline is especially common on smaller airliners and commuter planes. Whatever the location, the purpose of these steady white lights is to improve the plane’s visibility from behind the aircraft.
Anti-Collision lights: Two beacon lights are fitted to aircraft near the center of the fuselage. One is located on top of the fuselage and the other on the bottom. These lights are colored reddish orange and rotate to produce a flashing effect. The beacons are turned on just before the engines are started and they remain active until the last engine is shut down. The beacons help to serve as a safety warning to ground personnel that the engines are operational.
Strobe lights: High-intensity strobe lights that flash a white-colored light are located on each wingtip. Most smaller planes are only equipped with one of these strobes near the leading edge just behind the red or green navigation light. Larger airliners may be equipped with an additional strobe at the trailing edge as well. These flashing lights are very bright and intended to attract attention during flight. They are sometimes also used on the runway and during taxi to make the plane more conspicuous.