Europe has “maybe six weeks” of jet fuel left, the head of the International Energy Agency said, warning of possible mass flight cancellations as the Iran war hits global energy supplies.

The continent is by far the biggest buyer of jet fuel that is shipped through the Strait of Hormuz, leaving it exposed to foreign shocks: The UK, Europe’s leading jet fuel consumer, has just four refineries, down from 18 in the 1970s.

While carriers have hiked prices to reflect the 80% jump in fuel costs, IEA chief Fatih Birol warned the war may have permanently altered energy markets. “We are not going back to where we were” after the strait reopens, he said at Semafor World Economy this week.