By Rajesh Kumar Singh CHICAGO (Reuters) -U.S. carriers are struggling to offset higher costs even as booming travel demand has given them strong pricing power, raising questions about their ability to shield profit once consumer demand softens. Those worries are battering airline shares, taking the focus away from what is shaping up to be the industry’s strongest earnings season in three years. Shares of American Airlines Group Inc and United Airlines fell more than 9% on Thursday even after both carriers posted their first quarterly profit without U.S. government aid since the COVID-19 pandem…