Don't forget, there's actually two teams of Twins. There's the two who actually look alike (The Doublmint Twins) and there's that other team where the one brother is gay and the other one is straight.
Re: booking flights - according to the rules the teams actually have to book four seats on a flight. Two for them and two for their camera crew. If there's only two seats left on a flight, the team can't go.
I love this show, too. My friends have been threatened with death if they try to call me while its on. I like seeing the insides of airports around the world. I recognized CUN from when I was there 12 years ago.