Climate change threatens to ground aviation with more storms, delays and costly disruptions

On a Saturday in late June, as much of England baked under one of that summer's relentless heatwaves, towering thunderclouds began gathering over the south and across northern Europe. It was peak holiday season. Thousands of passengers were converging on London's Heathrow and Gatwick airports, ready to scatter across the continent. The day was always going to be busy. What unfolded instead was disruption on a scale that caught the industry's attention.

Air traffic controllers found themselves routing aircraft around storm cells as airspace became congested. Planes that should have been airborne sat waiting on tarmac. By the end of the day, roughly 900 flights to and from both airports had been delayed—some held up for as long as 11 hours. Dozens were cancelled outright. Across Europe, passengers expecting to land in London faced their own cascading waits and uncertainty. The weather has since cooled. Most travellers have moved on. But within the aviation industry, there is a growing conviction that June was not an anomaly. It was a preview.

Tim Atkinson, an airline risk consultant and former pilot, sees the incident as a warning about what climate change will do to one of the world's most congested airspaces. The skies over the UK and northern Europe are already packed. Add more severe weather, and the system becomes fragile in ways it has not had to be before. Atkinson sketches a scenario that keeps him focused: what if all of London's airports—Heathrow, Gatwick, Luton, Stansted—were hit by storms simultaneously? Aircraft diverted from one would seek landing slots at another, only to find it already full. Planes coming in from across the Atlantic and from across Europe would be circling, looking for anywhere to land, some with fuel reserves running low. The disruption to passengers would be severe. But the safety risk, he argues, could be worse. An aircraft running out of fuel in the sky is not merely an inconvenience. It is a catastrophe waiting to happen.

Not everyone shares this level of concern. Andrew Charlton, a former airline executive now running a Swiss aviation consultancy, thinks the risk remains low. He acknowledges the worst-case scenario is possible, but he also trusts the industry's ability to react and make sound decisions under pressure. Still, even Charlton concedes that if severe storms do become more frequent, airlines will have to adapt. They will carry more fuel as standard, factoring in the likelihood of unplanned diversions. Fuel is one of an airline's largest costs. If the fuel bill rises, passengers will pay. That is not speculation. That is arithmetic.

The physics of what is happening is straightforward. Thunderstorms form when moist air near the ground warms rapidly and rises. As it climbs, it expands and cools, and moisture condenses into clouds. Warmer air holds more moisture—roughly 7 percent more for every degree the Earth warms. The UK's Met Office does not predict more thunderstorms overall, but the ones that do form may be more violent and more impactful. Higher latitudes in the northern hemisphere are expected to see the biggest increases in conditions favourable for storm formation. Pilots will avoid flying through convective weather whenever possible. Storms produce turbulence intense enough to damage a plane's structure. Hail can crack windscreens or disable engines. But aircraft weather radars can only see about 320 nautical miles ahead, and thunderstorms move quickly. Diversions often happen late in a flight, burning extra fuel and creating cascading delays.

There are other climate threats to aviation that may prove harder to manage. Clear-air turbulence—violent air movement at high altitude with no visible warning—is becoming more common as the climate warms. Paul Williams, an atmospheric scientist at the University of Reading, notes that incidents over the North Atlantic have increased by 55 percent since 1979. Projections suggest severe turbulence could double, triple, or worse on many busy routes. On March 1, 2023, a Lufthansa flight from Austin to Frankfurt encountered what the airline called brief but severe turbulence. Passengers and crew were thrown around the cabin. The plane lost altitude suddenly and made an emergency landing in Washington DC. Seven people went to hospital. Such incidents remain rare, but they are becoming less so.

Rising sea levels pose a different kind of threat. When Hurricane Sandy hit the US East Coast in October 2012, storm surge flooded New York City and submerged the runways at LaGuardia Airport for several days. Before industrialisation, the kind of flooding that affected New York occurred roughly once every 500 years. Now it happens every 25 years or so. By mid-century, it could occur every five years. LaGuardia, built on reclaimed land next to Flushing Bay, is particularly exposed. It is not alone. According to research by Newcastle University, 269 airports worldwide are already at risk from rising sea levels, and that number is expected to climb. Airports in Amsterdam, London City, Bahrain, and Newark are among those most vulnerable. Protecting against such risks requires expensive investment in flood defences, raising runways, or relocating airports entirely. The Newcastle report estimates the cost could reach $57 billion. That bill will ultimately be paid by taxpayers or by passengers.

Gatwick Airport experienced severe flooding over Christmas 2013. Since then, it has spent tens of millions on mitigation strategies, though those figures pale beside the more than £2 billion it expects to invest in its current expansion. The aviation industry faces a paradox: it is criticised for its own contribution to climate emissions, yet it is also increasingly vulnerable to the climate change those emissions are driving. The global aircraft fleet is expected to double in size over the next two decades, even as the industry pursues a target of carbon neutrality by 2050. Charlton's assessment is blunt: the best the industry can do is mitigate. Airports need more space for disrupted passengers, more hotel rooms, more parking. But disagreeable moments are going to happen more often. Passengers, he says, will have to accept it as a fact of flying life.