Jet-fuel prices have surged more than 50% over the past year, pushing carriers to raise fares and Delta Air Lines Inc. DAL -0.91% to cut its profit expectations. Delta, the nation’s No. 2 carrier, said Wednesday it could take six to 12 months to recoup the extra fuel costs via pricier tickets. Fuel is again the single-largest expense for most airlines, accounting for about a quarter of operating costs. The recent run-up in prices echoes the jump seen from 2009 to 2011, which first spawned stand-alone surcharges on many international flights. Average domestic airline fares have fallen in each of the past four years, according to trade group Airlines for America, as carriers handed most of the fall in fuel prices back to passengers. Now, higher fuel costs have forced carriers to decide how much can be passed on directly to domestic fliers through higher fares or via surcharges […]