I was listening to this interview with David Shields, who played Everett Blakely.
He says while they were up in the planes in between takes, they would pass the time by giving each other riddles to puzzle out. The riddle scene in episode 3 was unscripted, just them chatting in between takes. And then it got worked into the show.
I'm sorry but this pic did make me laugh because everyone else looks like they're 1360% done (david looks slightly exasperated poor guy) and then there's nate smiling widely at the camera like a dork???