High traffic

Aircraft transmit their position, altitude (and much more) by Automatic Dependent Surveillance–Broadcast (ADS-B) transponders. This information is picked up by sensors on the ground and made available on the Internet. One notable service is The OpenSky Network. Anyone who is interested can set up their own ADS-B sensor and contribute to the network.

I wrote a script using the p5js JavaScript library that visualises some of this air traffic data.

476 aircraft over Switzerland, November 12, 2018, between 10:01 and 11:35 (94 minutes).
Each dot represents an aircraft position, 10 seconds apart.
Purple dots are aircraft at 10000 metres (30000 ft) or higher.
3080 aircraft over Europe, November 10, 2018, between 11:32 and 12:01 (29 minutes).
London appears to be the busiest airport.
One can see the limits of where the sensors reach, e.g. over the Bay of Biscay, west of France.
3D view at traffic (167 aircraft) over Zurich Airport, November 21, 2018, between 10:58 and 12:05 (67 minutes)

Update 2025: The OpenSky Network has since limited usage of its API, so this resource must be used more carefully now.

The Zurich sky on October 30, 2018

I was inspired for this project by looking at the sky, and noticing there were now more traces than in my childhood...

Also see The Cloud Appreciation Society.