Colorful lights cover taxiways and runways to help pilots navigate the airport. Red, blue, green, amber, and white lights glow, flash, and race across the ground. It’s time to find out what the colored airport lights mean and how pilots use them!
After an aircraft leaves the gate, the first challenge pilots face is navigating the plane to the runway for takeoff. Both day and night, airport lights make it easy to maneuver around the maze of taxiways.
Blue Lights: Taxiway edge lights are always blue. The blue taxi lights are easy to spot from the terminal and are often the first airport lights seen by passengers. Blue taxiway lights are typically illuminated after dark and during bad weather. For many airports, the blue lights are all that is necessary to mark the taxiways.
Green Lights: Green in-ground centerline lights are often installed at busy airports and airports that experience bad weather to enhance taxi guidance and safety. Unlike the blue lights used to identify the taxiway edges, green centerline lights are very bright. Pilots can see and follow them in the worst weather conditions, day or night.
The tough metal housings for in-ground lights are mounted flush with the surface of the taxiway. Only a small portion protrudes above ground. The lights are installed a few inches to the left or right of the actual painted centerline.
Although not technically airport lights, taxiway signs are well illuminated and easy to see. Yellow and black signs identify taxiways. A black background with yellow characters ( A3 ) identifies what taxiway the aircraft is on. A yellow background with black characters ( A4 ) identifies a crossing taxiway.
Red signs ( 31R ) always indicate a runway. The red color reminds pilots not to proceed without permission from an air traffic controller.
Runway Guard Lights
In the last few years, new types of lights have been added to enhance safety. One of the most prominent are Runway Guard lights. Introduced in 1995, these flashing amber lights warn pilots that they are about to taxi onto a runway.
The basic installation consists of a dual flashing light unit. One unit is mounted on each side of the taxiway where the aircraft must stop. Taxiing past guard lights onto the runway requires a clearance from air traffic control.
In addition to the dual flashing units, wig-wags are often installed in-ground, on the runway hold-short line. This system is really helpful during low visibility conditions.
Red Stop Bar Lights
Red Stop Bar lights (also known as Runway Status Lights) are another newcomer to the taxi light family. In an effort to reduce the risk of deadly runway collisions, Stop Bar lights are being installed at many airports world-wide.
The lights are placed along the hold-short line and are switched on and off automatically. Unlike the yellow guard lights which mean “use caution,” red stop bar lights mean STOP – Don’t even THINK about moving. When the lights are on, there is active traffic on the runway or landing imminently. The lights must be extinguished before an aircraft can proceed.
As of 2016, fifteen US airports have Runway Status lights installed with more on the way. Look for them at busy airports. They’re really bright; you can’t miss them.
Runways designed for low visibility operations (bad weather) have a lot of lights.
Note that not all runways have the same light configuration. The runway at St. Thomas, USVI, has only basic edge lighting because the weather is usually gorgeous. Foggy San Francisco, on the other hand, needs a full lighting system for low visibility weather.
Runway Edge Lights: The lights that mark the left and right edges of the runway are primarily white. The edge lights along the last 2000 feet of runway are yellow to let the pilots know that the end of the runway is approaching. This is useful information for both takeoff and landing.
Runway Threshold and End Lights: The beginning of the usable portion of runway is marked with a row of green threshold lights. Red lights mark the end of the runway.
Runway End Identifier Lights (REILs): To further highlight the beginning of the runway, two very bright strobe lights are installed to the left and right of the runway threshold. REILs are bright and can be seen for miles in good weather. Flashing REILs can even be seen while cruising at 35,000 feet. See if you can spot some on your next flight.
Runway Centerline Lights: Runways used for low visibility operations have white centerline lights installed every 50 ft to help pilots maintain directional control during takeoff and landing. Starting the last 3000 ft of runway, the lights alternate white and red. The last 1,000 feet of runway has solid red centerline lights.
Taxiway Lead-off Lights: To help pilots find the taxiway after landing, alternating green and yellow “lead-off” centerline lights are often installed. The Lead-off lights help flight crews quickly exit the runway.
When driving near an airport, it’s hard to miss dozens of orange light poles near the runways. The forest of lights are part of the Approach Lighting System.
There are several different configurations for approach lights. The type of instrument approach to the runway determines the design of the approach lights. Designs also vary in different parts of the world. The purpose of all the designs is the same: provide pilots with the visual cues necessary to properly align the aircraft for landing during bad weather.
The animated image is an example of ALSF-2 lights. The full name is “Approach Lighting System with Sequenced Flashing Lights – Configuration 2.” See why we use acronyms?
The white lights that appear to shoot toward the runway are called sequenced flashing lights. Pilots call them “the rabbit,” possibly named after the mechanical rabbit used during greyhound dog racing.
Runway rabbits are as bright as REILs and can often be seen during the cruise portion of the flight. They are another good light to watch for on a clear night when the in-flight movies are boring.
Touchdown Zone Lights
Approach lights guide pilots to the Touchdown Zone Lights (TDZL) on the runway.
Touchdown Zone lights consist of 30 rows of white lights on each side of the centerline down the first 3000 feet of runway. That’s 180 in-ground lights!
The purpose of the lights is exactly what you would guess from the name. Pilots want to touchdown within the touchdown zone to ensure adequate runway is available to stop the aircraft. If the aircraft will touchdown beyond this area, it’s time to go around and try again.
Advanced Airport Light Spotting: The PAPI
PAPI stands for Precision Approach Path Indicator. The PAPI is a set of four projectors that each contain a white light, red filter, and precisely adjusted lenses.
During final approach, aircraft fly about a 3 degree slope (glidepath) down to the runway. The PAPI gives pilots an easy way to visually verify that the aircraft is on the correct glidepath.
When the aircraft is above the correct glidepath, all four PAPI lights will appear white. Pilots will see four red lights if the aircraft is too low,
The PAPI displays two white and two red lights when the aircraft is on the correct glidepath.
As a passenger, the PAPI is a little more challenging to spot than other lights. Look for the four light array near the end of the runway. They can be located on either side. The best time to spot them is at the beginning of the takeoff roll or just before touchdown. When viewed from the ground, all four lights will be red.
When airborne, you might catch a glimpse of the PAPI as the aircraft turns onto final approach.
On a long final approach, it’s not uncommon to see four red lights. The pilots will maintain altitude until intercepting the 3 degree glidepath. The PAPI will then display two whites/two reds during final descent to the runway.
Keep your eyes open for the PAPI. The system is used all over the world. Bonus points if you spot PAPI’s cousin, the VASI.
Aerodrome (Airport) Rotating Beacon
Without a doubt, my favorite airport light is the granddaddy of them all: the Aerodrome Rotating Beacon. The origins of the beacon go back to the 1920’s. Most every airport in the US has one. Outside of the US and Canada, airport beacons are rare.
Aerodrome beacons operate from dusk to dawn. The beacons help pilots locate air fields and can be seen for miles. Public use airport beacons flash green and white.
In the United States, different flashing colors identify the type of facility. I had to memorize these when I was a student pilot:
- White and Green – Land airport
- White and Yellow – Water airport
- Green, Yellow, and White – Heliport
- White, White, Green – Military airport
- White, Green, Red – Hospital or Emergency Services Heliport
In Canada, many airports are identified by beacons that emit one white flash, 20-30 times/minute. Heliport beacons display a series of four quick white flashes (Morse code for the letter “H”), several times a minute.
If you’ve been keeping up, there’s a good chance you know way more about airport lights than Platinum-Level-Guy snoring in the aisle seat. Keep your eyes out the window and check out those lights.
You Might Also Enjoy:
The Savvy Passenger Guide to Airplane Lights
Everything you ever wanted to know about airplane lights!
More Information About Airport Lights:
FAA Aeronautical Information Manual (pdf)
Chapter 2: Aeronautical Lighting and Other Airport Visual Aids. Everything a pilot needs to know about airport lights, signs, and markings.
Can I Descend?
Overview of US approach lighting systems by Ranier Flight Service.
Runway Status Lights – Summary of system with video by the FAA.
Precision Approach Path Indicator – (Wikipedia)
Transcontinental Airway System – History of the 1920’s airway system.
FAA document: Design and Installation Details for Airport Visual Aids (pdf)
300 pages: Installation and specs of airport lights. For readers who like to dig deep.
A Quick Reference to Airfield Standards (pdf)
Chapter 2 discusses airfield lighting standards.