Biofuels, alternative flight routes and newer, green aircraft technology can make flying better for the environment. How close are we to introducing these climate-friendly alternatives?

Before the Covid-19 pandemic, when the global aviation sector was flying high in 2019, it contributed almost 6% of the planet-warming greenhouse gases in our atmosphere. A year later, with the industry crippled by pandemic-related flight cancellations, that figure had dropped by 43%. Last year, it was still 37% lower.

But air traffic has been steadily increasing, according to industry body the International Air Transport Association.

Greenhouse gas emissions are rising too. In response, the European Parliament has announced a proposal to introduce environmental labels for air travel from 2025. The system would serve to inform passengers about the climate footprint of their flights.

Carbon dioxide accounts for only about a third of the global warming effect attributed to air travel. Two-thirds is caused by other factors, most significantly the condensation trails, or contrails, aircraft leave behind.

Alternative flight routes could prevent contrails

Contrails — those narrow, white clouds that trace an airplane’s path through the sky — are formed when jet fuel, which contains kerosene, burns. At the average cruising altitude of between 8,000 to 12,000 meters (around 26,000 to 40,000 feet), low temperatures cause water vapor to condense around the soot and sulfur left behind by jet emissions. The resulting ice crystals can remain suspended in the air for hours.

Contrails trap heat in the atmosphere, much like in a greenhouse, greatly amplifying the impact of flying on the world’s climate. Recent studies have shown that contrails are around 1.7 times more damaging than CO2 emissions, when it comes to global warming.

On the plus side, contrails are relatively easy to avoid. Using satellite data, flight planners can optimise aircraft routes to avoid weather patterns that favour the formation of contrails. Pilots can also fly their jets 500 to 1,000 meters lower, for example, where temperatures aren’t as cold.

“It doesn’t require much effort to make these changes,” said Markus Fischer, divisional director at the German Aerospace Center, adding that it would mean between 1 to 5% more fuel and …