Twenty years ago, if you went into an airport you would walk up to a counter and present paper tickets to a human being. That person would register you on a computer, notify the flight you'd arrived, an check your luggage in. All this was done by humans. 

Today, you walk into an airport and look for a machine. You put in a frequent flier card or credit card, and it takes just three or four seconds to get back a boarding pass, receipt and luggage tag. What interests me is what happens in those three or four seconds. The moment card goes in, you are starting a huge conversation conducted entirely among machines. Once your name is recognized, computers are checking your flight status with the airlines, your past travel history, your name with the TSA (and possibly also with the National Security Agency). 

They are checking your seat choice, your frequent flier status, and your access to lounges. This unseen, underground conversation is happening among multiple servers talking to other servers, talking to satellites that are talking to computers (possibly in London, where you're going), and checking with passport control, with foreign immigration, with ongoing connecting flights. And to make sure the aircraft's weight distribution is fine, the machines are also starting to adjust the passenger count and seating according to whether to fuselage is loaded more heavily at the front or back.