​"We fear further flights will be cancelled, particularly by low-cost airlines and to destinations of lesser importance to tourism,​" Ralph Beisel, ADV’s chief executive, told the Sunday edition of Germany's Welt newspaper.

In the best-case scenario for 2026, passenger numbers would remain as they are. "In the worst-case scenario, some airports face a 10% drop in capacity. Extrapolated across all airports, that would affect 20 million passengers,​" said Beisel.

That would mean some destinations would no longer be served at all and others would have fewer flights which would cost more.

The war in Iran is disrupting oil shipments through the Strait of Hormuz, driving up the price of jet fuel and prompting some airlines to cancel flights.

​"Kerosene prices have been twice as high as before the war for more than two months. We do not expect the situation to return to normal in the coming months either,​" said Beisel.​"Even if kerosene is available, airlines will not be able to operate many flights profitably at these prices.​"

The warning comes amid wider disruptions across the global aviation industry, with airlines worldwide having cut roughly 13,000 flights and removed nearly 2 million seats from May schedules as carriers grapple with soaring fuel costs and operational uncertainty linked to the Middle East conflict.