S&P 500 opens at record after holidays, but airline shares slide following Covid cancellations<blockquote>标普500假期后开盘创历史新高，但航空公司股价因新冠疫情取消而下跌</blockquote>
U.S. stock indexes rose Monday as markets reopened after the Christmas holiday and investors assessed the spread of the omicron Covid-19 variant.The Dow Jones Industrial Average gained about 115 points, or 0.3%. The S&P 500 added 0.4% and the Nasdaq Composite ticked up 0.4%.Airline stocks fell after a holiday weekend that saw thousands of flights canceled due to Covid-related issues. The rampant spread of the omicron variant led to a staffing shortage at a time when airlines were looking to ramp