A passenger aircraft operated by Deutsche Lufthansa in Frankfurt, Germany, on April 13. The airline group — Europe’s largest — said it’s scrapping 20,000 uneconomic short-haul flights in the region this summer. | BLOOMBERG The Iran war has squeezed global supply of jet fuel, threatening to upend vacation plans as the peak summer travel season approaches in the Northern Hemisphere. The near-halt of shipping through the Strait of Hormuz has disrupted oil exports from the Persian Gulf, forcing refineries elsewhere to cut production of jet fuel and its base ingredient, kerosene. Compounding the problem, refiners in the Middle East, where more than 10% of the world’s jet fuel and kerosene is typically produced, have struggled to deliver cargoes to buyers outside the region. Jet fuel prices have risen even more than those of crude oil since the conflict started. They’ve surged to record highs, topping $200 a barrel in Europe.…