Aircraft draw delicate, virtual lines across the skies of Northern Ireland, the Republic of Ireland and Wales when they are captured by the ‘point merge’ system of Dublin Airport. | Photo: Jan Krummen

The wafer-thin strands across the image look like they’ve been drawn with a ruler – and as they move towards the centre, their perfect arcs could even have been made with a compass. But what looks like a highly intricate geometric drawing is in fact a record of the roughly 13,000 flights that landed at Dublin Airport in March 2024. Wales is situated at the bottom right, Dublin in the centre and Northern Ireland at the top left. Normally, such trajectories are simply recorded as numbers in a table, according to Jan Krummen, an aeronautical engineer researching at the Zurich University of Applied Sciences (ZHAW).

Each plane has what is called an Automatic Dependent Surveillance-Broadcast system (ADS-B for short) that monitors its flight, constantly transmitting its altitude, speed and position. “These data are not encrypted”, says Krummen. “And researchers can benefit immensely from them”. They can use them to analyse countless questions, such as how can air turbulence from aircraft taking off affect wind measurements on the ground, or how can fuel be saved by taking shortcuts. When you start a project using ADS-B, your first step is almost always to visualise the data, says Krummen: “The resulting structures often look really cool”. For the flight movements over Dublin, Krummen attributed each approach route a slightly different colour. “Then I played around with the thickness and the transparency of the lines”.

Krummen’s delicate network of lines was a prize-winner in the 2025 SNSF Scientific Image Competition. Its hint of symmetry in its filigree fanning has its origins in Dublin Airport’s use of the so-called ‘point merge’ process. “It’s still rather rare across the world”, says Krummen. It involves predetermining the curves that the aircraft fly at a fixed distance from a centre point (the ‘merge point’) before they all turn towards this point and head for the runway.

This system enables air traffic controllers to organise sequencing more efficiently, says Krummen: “On approach, the controllers have to ensure that predefined distances are maintained between aircraft”. He is fascinated by how this complex web of lines above Ireland seems to hint at other dimensions: “We see here something that is actually invisible to everyone, but which planes are sketching out above us every day in the heavens”.