Sustainability
How TUI Supports Research to Avoid Contrails
At TUI, we are committed to reduce the climate impact of our flights – both from CO₂ emissions and from so-called non-CO₂ effects. These non-CO₂ effects include emissions such as nitrogen oxides and water vapour. Among these, persistent contrails – formed when water vapour freezes high in the atmosphere – have the greatest climate impact. Contrails – the thin white lines sometimes trailing behind aircraft – may look harmless, but they can have a significant impact on global warming. TUI is actively supporting scientific research to better understand and reduce these effects, through real-world flight trials that demonstrate how persistent contrails can be avoided – without compromising safety or punctuality.
What Are Contrails – and Why Do They Matter for Sustainability?
Contrails (short for “condensation trails”) form when hot, humid engine exhaust meets cold, moist air at high altitudes – typically above 25,000 feet (around 8,500 meters). Ice crystals form and create the familiar white lines in the sky. Some contrails vanish quickly. Others persist for hours and spread into high-altitude cirrus clouds.
At TUI, we’ve proven that avoiding these areas works – without disrupting the passenger experience. Despite additional planning and occasional altitude changes, the average delay when flying around contrail zones was just two minutes. For passengers, flights remained smooth, safe, and on time. It only takes an active enroute climb or decent or maybe a short lateral rerouting to prevent flying through a zone of predicted persistent warming contrails.
TUI Takes Action: Contrail Avoidance Routing in Real Time
In just one week in February 2025, TUI analyzed more than 300 flights and changed the route of about a third to avoid persistent contrails – preventing an estimated 15,600 tons of CO₂e, equivalent to CO2 emitted on 250 return flights between Frankfurt and Cyprus. Despite the slight change of route, the plane needed only two minutes more on average. A new in-house analysis tool will soon deliver post-flight climate impact data to pilots.
How TUI Supports Contrail Science
TUI is an active partner in several international research initiatives that aim to better understand and reduce the climate impact of persistent contrails. This includes participation in large-scale programmes such as the “100 Flights Program” or “A4Climate”. Partners include the German Aerospace Center (DLR), Google, Contrails.org as well as universities, research institutes and technology providers across Europe. These projects combine flight data, satellite observations and advanced weather models to improve contrail prediction and avoidance strategies. By sharing our operational expertise and real-world flight results, TUI helps to turn scientific insights into practical solutions that can be scaled across the aviation industry.
The bigger picture
From the Flightdeck: An Interview with TUI Pilot Tony Schweigert
“Every flight feels like pioneering work.”
“We often climb or descend a bit more than on a normal flight. Even though we’re still in the research phase, every flight feels like a real contribution to something bigger.”
“At this stage, it’s all about data. If a flight adds valuable insight, that’s a success. But of course, my personal goal is always to fly without leaving a persistent contrail behind.”
“Unfortunately, we don’t have rearview mirrors in the cockpit. But we watch other aircraft at different altitudes. Sometimes we see them leaving contrails, while at our altitude, there’s nothing – and that’s a good sign. It tells us the models are working.”
“Absolutely. I have two young children – and climate protection and sustainability are close to my heart. It makes me proud to be part of a team that’s actively helping the industry change for the better.”
