Maybe like dogs and cats, United can chip people. Probably in the forearm. This way to enter the club, you just pass your wrist over a sensor, it reads your ID, and then verifies you are a club member against an internal database. They can also include a picture so that a picture comes up on the screen, so you don't have to lose three hours going back to your car or whatever for your ID.

Also, should you get amnesia, they can read your chip and just send you home.