Passenger flights could be grounded in the next two months because of a global shortage of aviation fuel caused by the Middle East war, industry experts warned on Thursday. Countries in Asia are likely to be affected first, followed by Europe. Both rely on oil from the Gulf and its refineries for their supplies.

“The situation can, within the next three, four weeks, become systemic,” energy economist Claudio Galimberti said. “So you can have severe cuts of flights in Europe, already starting in May and June.” Flights had already been canceled because of fuel shortages, he said.

German airline Lufthansa is closing its regional subsidiary because of higher fuel prices and industrial action. “The 27 operational aircraft of Lufthansa CityLine will be permanently removed from the flight program,” the airline said.