and home tests can be also difficult to find. a lot of uncertainty for those traveling tonight, and for the millions returning to work and school in the days ahead. dr. ashish jha joins us in a moment. but elwyn lopez leads us off. >> reporter: tonight, one of the busiest travel weekends of the year wrapping up with another day of mass cancellations. >> it's a long line, but what are you going to do. >> reporter: from coast to coast, 5 million passengers expected to hit the skies between today and tomorrow. >> i just want to get home. >> reporter: airports seeing more than 2,500 flights grounded. over 5,000 just this weekend. covid partially to blame, with an uptick in cases sparking staffing shortages. another major hit to operations -- that wintry weather from denver to chicago. >> we had a huge snowstorm. and, oh, my goodness, they cancelled the flight because they were scared that we wouldn't be able to take off. >> reporter: megan dillman managed to book another flight to atlanta for an event but is now worried about getting back home to chicago. >> well, i'm hoping that it doesn't get cancelled. because i'm not sure what i'm gonna do.