Once that's out of the way, the part that affects your luggage kicks in. A baggage tag is generated that includes date, flight number, destination, travel class, registration number and unique bar code. Your receipt, or baggage claim tag, is also printed. The ticket agent then tosses your bag onto a conveyor belt, which shuttles it into the airport's baggage sorting and handling system, where a laser scanner reads the bar code on the baggage tag and checks it against a database of departing flights. At most large airports, the bag passes through a security system, where it is X-rayed.
Different airports have different requirements.
At some airports, every bag is X-rayed. At others, bags are scrutinized at random, or only bags on certain flights go through the X-ray process. Once the bag has cleared security, it moves through the tracking system on a series of conveyors or shuttles until it reaches the proper loading bay. The bar code is scanned again to make sure that the bag has reached the correct flight. Before departure, the airline checks to make sure the number of people who checked in matches the number of passengers on board.