U.S. stocks fell on Monday on worries about the Omicron coronavirus variant ahead of a Federal Reserve meeting later this week, while investors watched Apple close in on $3 trillion in market capitalization. Seven of the 11 major S&P 500 sector indexes fell, with only defensive stocks including consumer staples, utilities, and real estate gaining. Travel-related stocks fell as the fast-spreading Omicron variant now accounted for around 40 percent of COVID-19 infections in London and at least one death in the United Kingdom. Carnival Corp.’s shares fell nearly 6.9 percent to lead declines among cruise operators, while the S&P 1500 airlines index shed 4.6 percent. “The big unknown is still the Omicron variant and we don’t know just yet how that may affect markets and the economy, but as long as that uncertainty exists the volatility is probably going to remain higher,” said Randy Frederick, managing director of trading and …