Threshold Light VS Wing Bar Light
Same Colour, Different Job — threshold lights identify the runway threshold across the runway width, while wing bar lights are additional threshold lights that extend outward from the runway sides to make the threshold more conspicuous. Both are part of runway threshold identification, but their position and purpose are different: one marks the threshold, the other makes it stand out.
At a Glance
| Feature | Threshold Light | Wing Bar Light |
|---|---|---|
| Main purpose | Identifies the threshold | Enhances threshold conspicuity |
| Location | Across/near the runway threshold | Extends outward from threshold toward the sides |
| Basic colour | Green, viewed from approach | Green, viewed from approach |
| Function | Marks start of landing area | Makes threshold more visually prominent |
| Arrangement | Transverse threshold row | Threshold row + outward extensions |
| Used alone | Yes, depending on runway type | Normally supplementary to threshold lights |
| Main benefit | Defines threshold | Improves recognition from approach |
| Lateral extension | Limited to runway threshold | Extends beyond runway edges |
One System, One Add-On
Threshold lights identify the beginning of the landing portion of the runway. Wing bar lights are installed as extensions of that same threshold lighting arrangement — additional threshold lights that project outward beyond the runway edges to widen and strengthen the visual signal a landing pilot sees.
What Is a Threshold Light & Wing Bar Light?
Threshold Light
Identifies the beginning of the landing portion of the runway. Forms a transverse row across the runway width, green when viewed from the approach direction.
Tells the pilot
- This is the runway threshold
- Landing may begin from this point
Wing Bar Light
Additional threshold lights that extend laterally beyond the runway edges, normally supplementary to the standard threshold row.
Tells the pilot
- The threshold is here
- Its location is made particularly conspicuous
Where the Name Comes From
Think of the threshold lighting line as the body of an aircraft shape, with the wing bars as the wings extending outward from it on either side. The additional lights extend outward like wings from the threshold lighting line — hence "wing bar," a lateral extension of threshold lighting.
Identification vs Conspicuity
Threshold Light
Tells the pilot: "This is the runway threshold." The core identification function.
Wing Bar Light
Tells the pilot: "The threshold is here, and its location/extent is particularly conspicuous." An enhancement, not a replacement.
Threshold light = identification. Wing bar = enhanced conspicuity.
Both Green on Approach
When viewed from the approach direction, threshold lights are green. Wing bars are also green when forming part of the threshold indication. The exact arrangement and colour requirements depend on the applicable runway lighting standard.
When Wing Bars Are Useful
Enhanced conspicuity: wing bars can be particularly valuable where the threshold needs to stand out against the surrounding background — during night operations, poor visibility, complex visual backgrounds, or on approaches requiring enhanced threshold conspicuity. They create a wider, more distinctive visual pattern than the threshold row alone.
Threshold, Wing Bar & Runway Edge — Three Different Roles
These three systems should not be confused. Runway edge lights are installed along the sides of the runway and define runway lateral limits. Threshold lights are installed across the threshold and identify the runway threshold. Wing bars extend outward from the threshold line specifically to enhance threshold conspicuity — a distinct purpose from all-along-the-runway edge marking.
Wing Bars and the Displaced Threshold
This distinction becomes particularly important with a displaced threshold, where the threshold does not coincide with the physical beginning of the runway pavement. Threshold lighting identifies the actual threshold rather than simply the beginning of pavement — and wing bars, where specified, reinforce this visual identification at the correct point.
Threshold Light vs Wing Bar Light
| Parameter | Threshold Light | Wing Bar Light |
|---|---|---|
| Primary role | Identify threshold | Enhance threshold conspicuity |
| Position | Across threshold | Extends laterally from threshold |
| Approach colour | Green | Green |
| Runway edge | Inside/at threshold | Extends beyond runway sides |
| Visual pattern | Transverse line | Wider transverse pattern |
| Required on every runway | Depends on runway type/standard | Not universally required |
| Installation | Standard threshold lighting | Supplementary arrangement |
| Main advantage | Clear threshold identification | Greater conspicuity |
Common AGL Terminology Confusion
Wing bars are additional threshold lights — a lateral extension of the same threshold indication, not an independent system with its own separate function.
Wing bars are normally supplementary and not universally required; whether they are installed depends on the runway type and the applicable lighting standard.
Wing bars are also green when viewed from the approach direction, matching the threshold indication — the difference is position and conspicuity, not colour.
Threshold Light vs Wing Bar Light
Threshold and wing bar lights are not competing systems — wing bars are a supplementary extension of threshold lighting. The fundamental difference is position and purpose, not colour or basic function.
Threshold lighting identifies where the landing portion of the runway begins; wing bar lighting widens that same indication so the threshold is more conspicuous on approach.
Easy memory: Threshold = "where landing starts." Wing bar = "make the threshold more visible."
Engineering & Expert Notes
Verify Green Colour on Both
ColourCheck chromaticity.
Check Positions Against Survey
PositionVerify layout.
Check Orientation
OrientationVerify direction.
Inspect at Night
InspectionLook for gaps.
Frequently Asked Questions
Position and purpose — threshold lights form the main transverse row identifying the threshold, while wing bar lights are additional lights that extend outward beyond the runway edges to make that same threshold more conspicuous.
No. Both are green when viewed from the approach direction. Wing bars form part of the overall threshold indication rather than presenting a separate colour.
No. Wing bars are normally supplementary to threshold lights, and whether they are installed depends on the runway type and the applicable lighting standard.
Because the additional lights extend outward from the threshold lighting line like wings on either side, widening the visual pattern the pilot sees on approach.
Yes. Threshold lighting identifies the actual threshold rather than the physical start of pavement, and wing bars, where specified, reinforce that visual identification at the correct point.
No. Runway edge lights run the length of the runway and define its lateral limits. Wing bars are localized to the threshold area and extend outward specifically to enhance threshold conspicuity.
Governing Documents
For an actual project design, always verify the current edition of the applicable documents.
ICAO Annex 14, Volume I
Aerodrome Design and Operations — runway threshold and wing bar lighting colour, siting, extent and applicability requirements.
FAA AC 150/5340-30
Design and Installation Details for Airport Visual Aids — threshold and wing bar lighting configuration, installation and photometric requirements.
DGCA / AAI Requirements
For Indian airport projects, also verify applicable DGCA requirements, AAI requirements, airport-specific technical specifications, project drawings and contract specifications.
Final Engineering Note
Do not design a threshold or wing bar lighting arrangement from a generic web diagram. The final installation drawing should always be developed from the current governing standard, approved airport design and project-specific requirements.
Threshold = the main green identification row. Wing bar = a supplementary green extension that makes the same threshold more conspicuous.
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