Runway lighting explained: approach lights, PAPI and the color codes at the airport

After sunset, an airport turns into a sea of colored dots: white strings of lights, green lines, red rows, blue edges, and a pulse of light shooting out of the darkness toward the runway. That’s no coincidence and no decoration. Runway and taxiway lighting follows an international color code that pilots read the same way all over the world. Once you know it, you understand a lot more at the fence at night: which runway is active, where aircraft turn off, why a jet is waiting at the holding point. And you quickly find new subjects for your night photos.

Runway lighting: the short answer

The lighting at a commercial airport consists of four building blocks. The approach lighting guides the aircraft from outside the airport grounds onto the runway centerline. The glide slope indicator (PAPI or the older VASI) shows whether the descent is too steep or too shallow. The runway lighting marks the threshold, edges, centerline, touchdown zone and end. The taxiway lighting guides aircraft on the ground to the gate and back.

The basis is Annex 14 of the International Civil Aviation Organization (ICAO), implemented in Europe through EASA’s aerodrome design rules. The USA has its own FAA systems, which differ in details. The color code itself is almost the same everywhere.

The color code at a glance

Before we get into the details, here is the overview. With this table, you can immediately place most of the lights at an airport at night.

Color	Where you see it	Meaning
White	Runway edge, runway centerline, touchdown zone, approach lighting	Runway and approach axis
Green	Landing threshold, taxiway centerline	Start of the landing zone, guide line on the ground
Red	Runway end, stop bars, parts of the centerline at the runway end	End, hold, stop
Yellow	Last section of the runway edge, holding position warning lights, centerline at crossings	Caution, transition, the runway is coming up
Blue	Taxiway edge	Edge of taxiways and apron areas
Red/white	PAPI	Glide path too low (red) or too high (white)

Approach lighting: lights in front of the fence

The approach lighting system (ALS) doesn’t begin at the runway but far in front of it. It consists of rows of lights on the extended runway centerline, mostly on masts that stand out over fields, roads or water. For ICAO Category I precision approaches, it extends up to about 900 meters before the threshold. If you stand at spots under the approach path, you often have these masts right in front of your lens – what to watch out for there is covered in the guide Spotting under the approach path.

Why the effort? On an instrument approach, for example via ILS, the crew flies down to a decision height by instruments. There they must have visual contact with the runway or its surroundings, otherwise they go around. The approach lighting is often the first thing that emerges from haze or clouds. It immediately shows whether the aircraft is on the centerline and how far away the threshold still is. In the USA, for example, an existing approach lighting system allows lower visibility minima than an approach without one.

Crossbars and systems

Typical for the systems in Europe are crossbars: short rows of lights across the centerline that look like a horizon and tell the pilot about the bank angle. The British Calvert system, on whose pattern many ICAO installations are built, uses several such bars. In the USA, the installations have abbreviations like ALSF-2, MALSR or SSALR; all of them have a striking decision bar about 1,000 ft before the threshold.

For approaches in very poor visibility (Category II and III), additional elements come into play, including red side rows over the last few meters before the threshold. For you as a spotter, that means an especially elaborate approach lighting system shows the runway is equipped for fog landings.

The “rabbit”

Many installations have sequenced flashing lights that light up one after the other – from the outer end toward the runway, about twice per second. The pulse of light seems to run toward the runway; pilots call it the “rabbit.” The chain of flashes ends before the transition to the steady lighting so that it doesn’t distract in the final phase. Photographically, it’s a gift: with long exposures, the flashes become bright rows of dots that emphasize the centerline.

PAPI and VASI: the traffic light for the glide path

Beside the runway, usually on the left and a few hundred meters beyond the threshold, there is a row of four boxes. That is the PAPI (Precision Approach Path Indicator). Each unit shines white upward and red downward, and the switching angles are slightly staggered. On a 3-degree approach, they typically lie between 2 degrees 30 minutes and 3 degrees 30 minutes. The system was developed in the 1970s at the British Royal Aircraft Establishment in Bedford.

What the pilot sees	Meaning
4 × white	clearly too high
3 × white, 1 × red	slightly too high
2 × white, 2 × red	on the glide path
1 × white, 3 × red	slightly too low
4 × red	clearly too low

Smaller airfields have a scaled-down version with two units (A-PAPI). The predecessor is called VASI: two light bars standing one behind the other, where “red over white” indicates the correct path. Pilots have a mnemonic for it: “Red over white, you’re all right.” VASI installations are gradually being replaced by PAPI worldwide.

From the ground, you usually only see the red part of the PAPI or nothing at all – the lights shine in a targeted way obliquely upward into the approach. In aerial photos, for example from the airplane window, they are easy to spot.

Runway lighting in detail

On the runway itself there are several groups of lights. Which of them are installed depends on the approach category the runway is certified for.

• Threshold lights (green): A row of green lights across the runway marks the landing threshold. From here, touchdown is allowed. If the threshold is displaced, the green line sits correspondingly farther in. Sometimes green wing bars at the sides are added.
• Threshold strobe lights (white): One strobe light each on the left and right of the threshold, flashing in sync, make the start of the runway easy to find at night.
• Edge lights (white/yellow): White lights stand along both runway edges. On instrument runways, they change to yellow in the last section, according to ICAO on the last 600 meters or the last third, whichever is shorter. Yellow here means: the end is coming.
• Centerline lights (white/red): In-pavement lights on the centerline. They are white until 900 meters before the runway end, then alternate between red and white, and on the last 300 meters they are red. A pilot taking off or landing thus sees how much runway is left without doing mental math. They are required mainly for approaches in very poor visibility.
• Touchdown zone lights (white): Paired rows of short white light bars left and right of the centerline on the first 900 meters beyond the threshold. They mark the area where the aircraft is supposed to touch down and are part of the equipment for Category II and III.
• End lights (red): A red row across the runway marks the end of the usable runway. For an aircraft taking off or landing, it lies at the far end; threshold and end lights often sit in combined units that shine green to one side and red to the other.

How the runway numbers at both ends come about is explained in the guide Runway designations at the airport. Together with the lighting, you can easily estimate at night where on the runway an aircraft currently is.

Taxiway lighting: blue, green and the important red

As soon as an aircraft leaves the runway, the color scheme changes. So that nobody accidentally taxis onto a runway, taxiways are marked differently.

• Edge lights (blue): Blue lights line taxiways and apron edges. If you look at an airport at night and see blue lines, it is almost always a taxiway.
• Centerline lights (green): Green in-pavement lights show the way like a guide line. At large airports, individual sections are deliberately switched on and off so that a green trail runs ahead of the aircraft all the way to its destination.
• Exit taxiways (green/yellow): Where a rapid exit taxiway leaves the runway or a taxiway crosses it, the centerline lights alternate between green and yellow. This marks the area where the aircraft is still close to the runway.
• Stop bars (red): The stop bar is a row of red in-pavement lights across the taxiway at the holding point before the runway, sometimes with elevated red lights at the sides. When it is lit, that’s the end of the line. With clearance, air traffic control switches it off and the green lights beyond it come on.
• Holding position warning lights (yellow): Flashing pairs of yellow lights to the left and right of the taxiway or a row of yellow in-pavement lights point to the holding position before a runway. Pilots know them as “wig-wags.”

What the letters and signs on the taxiways mean is covered in the article Taxiways, holding points and signs. If you also listen to the radio, you quickly understand why an aircraft waits in front of the red bar: the takeoff clearance comes from the tower, the taxi instructions from Ground or apron control – more under Delivery, Ground, Tower, Approach.

What the lights tell you at the fence

By day you see aircraft, at night you mostly see light. The color code still lets you read a lot.

The lights on the aircraft itself – navigation lights, landing lights, anti-collision lights – follow a code of their own. How to recognize aircraft at night by these lights is explained in the guide Recognizing aircraft at night.

Runway lighting as a photo subject

For night shots at the airport, the lighting is often the real subject. A few ideas that work at many spots:

• Light trails over the runway: With exposure times of several seconds, the landing lights draw a line over the approach lighting – the colorful runway lights form the frame. A tripod is a must.
• Blue hour: Shortly after sunset, the sky is not yet black but the lighting is already on. Colored light against a dark blue sky is a classic, see Golden hour and blue hour.
• Telephoto shots of the approach line: With a long focal length, the light masts compress into a chain with the aircraft hanging above it on final approach.
• Stop bars and taxiways: From observation decks and elevated spots you see the taxiway lines as green and blue ribbons. A taxiing aircraft between them makes for a nice image composition.

Technical basics on exposure, ISO and tripod can be found in the article Photographing aircraft at night. Also keep operating hours in mind: at many German airports, traffic largely rests at night, details at Night flight bans at German airports. The evening hours and early morning are therefore usually more productive than the time after midnight.

Elevated spots with a view over the runway system are especially suited for lighting shots, such as the Munich Airport visitors’ hill or the Zeppelinheim viewing platform at Frankfurt Airport. Check beforehand whether the spot is accessible in the evening.

Common misconceptions

• “Red lights mean danger.” Not necessarily. At the airport, red mostly marks ends and holding points. The red obstruction lights on masts, cranes or hangars belong to a different system anyway.
• “Every runway has centerline lights.” No. Many smaller runways only have edge, threshold and end lights. Centerline and touchdown zone lights are found mainly on runways equipped for approaches in poor visibility.
• “I can see the PAPI from the ground.” Usually only to a limited extent, because the lights are focused into the approach. From the ground they often look red or dark.
• “The lighting is identical everywhere.” The color code is largely the same internationally, but the actual installations differ between ICAO and FAA systems and from airport to airport.

Who operates the lights?

The lighting is part of the airport operator’s infrastructure, but it is controlled in close coordination with air traffic control. The brightness is adjusted to visibility and time of day, and taxiway sections and stop bars are switched depending on traffic. In Germany, DFS Deutsche Flugsicherung (the German air navigation service provider) is responsible for control at the large airports, while the apron is partly monitored by the airport itself. At large hubs like Munich Airport, the lighting is a large technical system that is continuously checked and maintained.

Conclusion

An airport’s lighting is a guidance system with a clear language: approach lights and strobes lead onto the centerline, the PAPI shows the glide path, green and red mark the start and end of the runway, yellow warns of transitions, blue and green guide along the taxiways, and red across the taxiway means stop. If you know this code, you understand night operations much better and find subjects that nobody sees by day.