Within a few years, you might no longer be using paper boarding passes to go through airport security checkpoints. Instead, you might be registering your cell phone number with your airline to receive a text message with a boarding pass bar code. You might then be holding up the screen of your cell phone under the airport security scanner, rather than show a paper record. Air Canada, Air Berlin, ANA, and Spanair already offer the service in their countries, and U.S. airlines are pressing for government approval to offer the same service here. It might save them some money.