Many of the biggest U.S. airlines are cutting flights and raising fares to counteract rising fuel prices that are threatening a long run of profitability . American Airlines Group Inc. AAL 4.79% and Southwest Airlines Co. LUV 8.43% joined rivals in trimming capacity growth for this fall, spurring a rally on Thursday for airline shares that have fallen sharply this year. U.S. carriers had been adding aircraft and flights at a rapid clip, pressuring fares and profits even as demand remained strong in the face of spiking fuel costs. American, the world’s largest airline by revenue, on Thursday trimmed its profit outlook for 2018 and pledged to cut capacity and delay delivery of some new Airbus SE jetliners after fuel costs rose 40% in the second quarter compared with last year. “To the extent any of us were viewing this quick run-up as a spike that would quickly correct […]