The jet-fuel crisis is turning into a disaster for airlines.  Across the world airlines have been trying to deal with rising fuel costs that are threatening to add billions of dollars in unexpected expenses this year, and forcing carriers to raise fares and trim routes to stem their mounting costs. Budget carriers are especially squeezed. At Spirit Airlines’s headquarters in Florida, members of the operations team gathered in a war room late Friday to track the company’s final flights. Spirit had been hemorrhaging the cash it needed to escape bankruptcy. The airline shut down operations after its efforts to gain relief from the U.S.…