Jet fuel shortages threaten to disrupt summer travel as the loss of supplies from the Middle East ripples across Asia and Europe. Exports from the Persian Gulf represented the largest single source of jet fuel supply to the global market before the U.S. and Israel attacked Iran on Feb. 28, according to the International Energy Agency . Iran's blockade of the Strait of Hormuz has cut off those jet fuel exports from the world. Europe is directly affected because the continent was the biggest