“Once they would have gotten to the airport, Kevin would have had to have been there and accounted for his ticket to get on the plane.”
Except they threw out Kevin’s ticket. https://www.buzzfeed.com/ryanhatesthis/one-thing-that-youve-definitely-never-noticed-about-home-alo?utm_term=.vka1wrbRwM#.jsmm2J7l2a
So when they get to the airport, all the tickets match all the people.
