Why are more flights cancelled in summer? The causes explained
27 March 2026
Why are more flights cancelled in summer? The causes explained
Every year between June and September, the news fills with stories of passengers stranded at airports, cancelled flights and cascading delays. It’s not just a perception: EUROCONTROL data confirms that summer months consistently record the highest number of aviation disruptions in Europe. But why does this happen precisely when everyone wants to fly?
The causes are multiple and interconnected. Understanding them won’t spare you the disruption, but it helps you make more informed decisions when booking your next summer flight.
1. Summer weather is more unstable than you’d think
Summer conjures blue skies, but meteorologically it’s the most unpredictable season for air transport in Europe. Daytime heat generates convective thunderstorms — those towering clouds that form in the afternoon and unleash intense rain, hail and lightning.
Unlike winter bad weather, which is predictable days in advance, summer thunderstorms form rapidly and hit limited areas. A cumulonimbus over Milan Malpensa airport can block departures and arrivals for an hour or two, generating delays that propagate to dozens of other flights.
The areas most affected in Europe:
- Po Valley (Milan, Verona, Venice) — one of the areas most prone to convective thunderstorms
- Adriatic and Tyrrhenian coasts in the afternoon
- Central Europe (Munich, Frankfurt, Zurich)
- Eastern Spain (Barcelona, Palma)
2. Air traffic at record highs
Summer is peak season. Airlines increase frequencies, add seasonal routes and fill every available slot. According to EUROCONTROL data, European air traffic in summer exceeds 35,000 flights per day, compared to around 25,000 in winter months.
More flights mean:
- Less margin for air traffic controllers
- Tighter slots for takeoffs and landings
- Longer queues at the gate, on the runway, in the air
- Amplified domino effect: a delay propagates faster when the system is at its limit
The main bottlenecks are hub airports and the busiest air corridors, such as the one crossing southern France and Switzerland connecting northern Europe to the Mediterranean.
3. Staff shortages
The COVID-19 pandemic left a deep mark on the industry. Between 2020 and 2021, airlines, ground handlers and airport managers cut thousands of jobs. When demand exploded again in 2022, the industry wasn’t ready.
Years later, the situation has improved but isn’t fully resolved. The problem isn’t just the number of employees, but training: training an air traffic controller takes years, training qualified ground staff takes months. During peak season, the system operates with very thin margins.
The consequences:
- Longer baggage check-in times
- Delays in catering and refuelling
- Longer boarding times
- Less flexibility in handling unexpected events
4. The low-cost model and tight turnarounds
Low-cost airlines like Ryanair, easyJet and Wizz Air operate on a model built around extreme efficiency. A Ryanair aircraft spends an average of 25 minutes on the ground between arrival and the next departure. This means a single aircraft can operate 6-8 flights a day, maximising revenue.
The flip side: with such tight turnarounds, there’s no margin for the unexpected. A 30-minute delay on the first flight of the day generates a domino effect that carries through until evening. And in summer, with afternoon thunderstorms and high traffic, initial delays are nearly the norm.
Full-service carriers (Lufthansa, Air France) have longer turnarounds and larger fleets, so they can absorb delays better. But even they aren’t immune: their hubs (Frankfurt, Paris CDG, Amsterdam) are among the most congested airports in Europe.
5. The domino effect
This is perhaps the least intuitive aspect. European air transport is an interconnected system: the same aircraft operates flights in different cities throughout the day. If your 18:00 flight from Rome Fiumicino to Berlin is operated by an aircraft that morning flew from Berlin to London and London to Rome, a problem in London at 10:00 becomes your delay in Rome at 18:00.
In summer, with the system at its limit, these cascading effects are more frequent and more severe. A thunderstorm over Paris CDG at 14:00 can cause delays in Barcelona, Milan and Amsterdam by evening. Not because the weather is bad in those cities, but because the aircraft that were supposed to arrive from Paris are stuck.
How to protect yourself
You can’t control the weather or airlines’ staffing decisions, but you can make choices that reduce the risk of disruption.
Book morning flights
Early morning flights (before 9:00) statistically have fewer delays. The aircraft is already at the airport from the night before, summer thunderstorms haven’t formed yet and the system hasn’t yet accumulated delays. If your flight allows it, prefer the 7:00 departure over the 17:00 one.
Avoid the most congested hubs for connections
If you need to connect, choose airports with less traffic. A layover in Lisbon or Helsinki has less chance of generating delays than one in Frankfurt or Paris CDG. If you can, take a direct flight.
Leave margin for connections
If you need a connecting flight in summer, don’t book with the minimum allowed layover. Add at least an extra hour beyond the minimum. If you miss the connection due to a delay on the first flight, the airline must rebook you — but you could lose hours or a whole day.
Keep an eye on the signals
The conditions that cause summer disruption are largely predictable: weather forecasts, active NOTAMs, ATC delays, route history. Monitoring them in the days before departure gives you a realistic picture of what to expect.
The numbers
To give an order of magnitude, during summer months in Europe:
- About 30-35% of flights experience a delay of more than 15 minutes
- The average delay for delayed flights is about 30-40 minutes
- Cancellations affect 1-2% of total flights
- The worst days are Fridays and Sundays, when leisure traffic combines with business traffic
These aren’t catastrophic numbers, but with over 35,000 flights a day, even 1% cancellations means hundreds of suppressed flights and tens of thousands of affected passengers every day.
Sources
Want to know if your next flight is at risk? Check the risk of your flight on FlightGuard.