Jackson Ripner: Do your dad a favor and stop gambling with his life!
Lisa Reisert: Is it Jack for short?
Jackson Ripner: No. I haven't gone by Jack since I was ten years old. Last name's Ripner.
Lisa Reisert: Jack Ripner... Jack the... Oh!
Jackson Ripner: There you go.
Lisa Reisert: That wasn't very nice of your parents.
Jackson Ripner: That's what I told them. Before I killed them.





Answer: These are tech-savvy terrorists. Not only were they closely watching Keefe, but also Lisa, who is integral to their assassination plot. The assassins were monitoring their every move, intercepting cell phone calls, probably hacking into the hotel's and the airline's computers, and so on. It is unknown how Jackson got a seat right next to Lisa, but as it's a late-night Red Eye flight, there would likely be fewer passengers and he could have managed to be seated next to her or somehow got the airline to switch him with another passenger.
raywest ★