Stand at the end of any airport runway after dark and you will see a light show that looks random but is anything but. Every flash, every colour, every steady glow on an aircraft has a specific purpose, a regulatory requirement, and a logic that pilots read as instinctively as you read road signs. Once you understand the code, you can look at any aircraft in the night sky and know which direction it is heading, whether it is climbing or descending, and whether its engines are running — all without hearing a word from air traffic control.

The Big Three: Red, Green, and White

Navigation lights are the foundation. Every aircraft is required to display three: a red light on the left (port) wingtip, a green light on the right (starboard) wingtip, and a white light on the tail. These are steady, not flashing, and they are required from sunset to sunrise and in any conditions of reduced visibility.

The system was borrowed directly from maritime navigation. Ships have used the same red-left, green-right convention since the 1840s, when it was adopted to prevent collisions in busy shipping lanes. Aviation inherited it when aircraft first began flying at night in the 1920s, and it has not changed since.

The beauty of the system is that it instantly tells you which way the aircraft is going. If you see a red light on the left and a green light on the right, the aircraft is flying toward you. If the positions are reversed — green on the left, red on the right — it is flying away. If you see only a red light, it is crossing from right to left. Only green? Left to right. And if all you see is the white tail light, you are behind it.

The Flashers: Beacons and Strobes

The rotating red beacon — the steady, rhythmic pulse you see on the top and bottom of the fuselage — serves a different purpose entirely. It is the aircraft’s “I’m alive” signal. Pilots turn on the beacon before starting engines and leave it on until the engines are shut down after parking. If you see a red beacon rotating on a parked aircraft, it means the engines are about to start or are already running. Ground crews treat it as a warning: stay clear.

Strobe lights are the high-intensity white flashes on the wingtips and sometimes the tail. These are the most visible lights on the aircraft — designed to be seen from miles away — and they serve as anti-collision lights in flight. Most airlines turn strobes on when entering an active runway and off when clearing the runway after landing. Some pilots leave them on throughout the entire flight.

If you have ever noticed a particularly aggressive white flash on a plane overhead, that was a strobe. They are deliberately intense. In the air, conspicuity saves lives.

Landing and Taxi Lights

The powerful white lights you see on an aircraft’s nose or wing roots during approach are landing lights — essentially high-powered headlamps that illuminate the runway environment during the final stages of flight. Most airlines require them on during takeoff and approach, and many keep them on below 10,000 feet as an additional “see and be seen” measure in busy terminal airspace.

Taxi lights are similar but less intense, aimed downward to illuminate the taxiway surface. They help pilots navigate the airport’s network of taxiways, especially at night or in low visibility when the painted centreline and edge markings are the only guidance. Runway turnoff lights, mounted in the nose gear area on some aircraft, illuminate the area directly ahead of the nosewheels during high-speed exits from the runway.

The Fancy Ones: Logo and Wing Inspection Lights

Not every light on an aircraft is about safety. Logo lights — mounted on the horizontal stabiliser and aimed at the airline’s tail logo — exist purely for branding. Airlines want passengers and spotters to see their livery during night operations. It is advertising at 200 knots.

Wing inspection lights, mounted on the fuselage and aimed at the leading edge of the wings, serve a more practical purpose. Pilots can switch them on to check for ice accumulation on the wings during flight in icing conditions. A quick glance out the window at an illuminated wing leading edge can confirm what the ice-detection instruments are reporting — or reveal icing that the sensors have missed.

Reading the Night Sky

The next time you see an aircraft at night — whether from the ground, from another plane, or from an airport terminal window — try reading its lights. Red on the left and green on the right means it is coming toward you. Strobes flashing means it is in active flight. A red beacon rotating on the ramp means engines are running. Landing lights blazing means it is below 10,000 feet or on approach.

Every light tells a story. Once you know the language, the night sky is full of conversations.

Sources: FAA Advisory Circular AC 20-30B, Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B), International Maritime Organization lighting conventions