These Red and White Lights Save Thousands of Lives — Here’s Why Airports Use PAPI!

If you’ve ever looked out the airplane window during landing, you might have noticed a row of red and white lights beside the runway.

These are PAPI lights — and they do much more than just look cool.

They are a pilot’s most trusted visual guide when approaching a runway.

What Are PAPI Lights?

PAPI = Precision Approach Path Indicator

It’s a system of 4 lights placed beside the runway that tells pilots if they are:

• Too high
• Too low
• On the perfect glide path

It works like a color-coded visual altitude indicator, allowing for a safe, precise, and smooth landing.

How PAPI Works

The lights show different colors depending on the approach angle:

• All White Lights: You’re too high
• 3 White / 1 Red: Slightly high
• 2 White / 2 Red: Perfect glide path (ideal)
• 1 White / 3 Red: Slightly low
• All Red Lights: You’re too low

Tip for passengers: If you see mostly white, the plane is above the correct descent angle.

Why Are PAPI Lights So Important?

1. Safety in all conditions
• Especially in poor visibility, fog, or night approaches.
• PAPI provides a visual confirmation of glide path.
2. Reduced risk of undershooting or overshooting
• Pilots avoid hitting obstacles or landing short.
3. Consistency across airports
• Standardized internationally — pilots can rely on the system anywhere.
4. Supports automatic systems
• Works alongside autopilot and ILS, providing extra safety.

These Red and White Lights Save Thousands of Lives — Here’s Why Airports Use PAPI!

Where Are PAPI Lights Used?

• Most international airports
• All CAT II/CAT III runways
• Military airbases

They are usually on the left side of the runway for visibility from the cockpit.