Alaska Airlines said Thursday it will trim its schedule by about 10 percent for the rest of January as it deals with “unprecedented” numbers of employees calling in sick during the current COVID-19 outbreak. The move by Alaska is similar to a decision last week by JetBlue Airways to cut about 1,300 flights through mid-January. Alaska’s announcement came on a day in which more than 2,100 U.S. flights were canceled by early evening on the East Coast, according to FlightAware. The tracking service said that equaled about 8 percent of the day’s scheduled flights, and it was the 12th straight day of 1,000-plus cancellations, which airlines blamed on the virus surge and winter weather. Worldwide, airlines had canceled about 4,700 flights. Southwest continued to be the hardest hit among U.S. airlines, canceling about 650 flights, or 21 percent of its schedule for Thursday by early evening. A spokesman said the …