Kara's clothes fit Jessie perfectly although Jessie is taller.
The American Airlines gate rep advises a customer the flight was fully booked. However, there are several obvious empty seats near Jessie and Kara.
All of the airport scenes are filmed at the Stillwater Regional Airport, so technically, the girls are taking off from and landing at the same airport. Although it is served by American Airlines, they plan they are on is not the type of regional jet that flies into and out of Stillwater.
The film is supposed to take place at Christmas but at 1:10 Jessie's mobile phone rings and by the visible display it was Saturday, February 25, 2017.
Near the end, Roy is seen twice by the Christmas tree, shaking a gift box and stacking it back up; it's obvious that it's the same footage.
When Kara looks out the window and says "Hey guys, it's the Christmas star. Let's all go outside and make a wish," as they leave the house the star is so high up in the sky and almost directly above the house, that Kara never would have been able to see it from the downstairs window.