U.S. stock index futures inched higher on Monday, boosted by megacap companies, while hundreds of Omicron-driven flight cancelations kept investors on edge at the start of this year’s final trading week. Travel-related stocks, typically sensitive to news around the coronavirus, slid after U.S. airlines called off many flights for a third day on Sunday as surging COVID-19 cases forced Christmas weekend travelers to change plans. Delta Air Lines, United Airlines, American Airlines, and Southwest Airlines dropped between 1.5 percent and 2.8 percent premarket. Cruise operators Norwegian Cruise Line Holdings, Royal Caribbean, and Carnival Corp. fell 2 percent-2.8 percent. The S&P 500 closed at a record high on Thursday, as upbeat news related to the Omicron coronavirus variant calmed investor nerves over the highly infection strain’s economic impact after it upended markets earlier this month. Wall Street’s three main indexes are eyeing a third straight yearly gain, with the benchmark S&P …