Both the Cubs and White Sox use United Airlines charters for their travel needs, and United always assigns them the same flight numbers: 9904 for the Sox, 9907 for the Cubs.
And therefore, it’s possible to track their flights: 9904 and 9907. Because it’s a charter service, you’ll see some airports that aren’t normally served by United but that are closer to the hotel or stadium: Wheeler Downtown Airport in Kansas City to meet the Royals, for example, or St. Petersburg/Clearwater International for Rays games.