For much of the past decade, boarding passes have used barcodes. Seemingly random bits of black and white that a scanner reads and identifies with your seat, flight number, travel date and name. Matching this information with your ID then ensures you paid for a particular seat on the plane. The mobile phone simply replicates that barcode on-screen and replaces a printed barcode.
Those flying from Contintental's hub city will still need a boarding pass -- for their return flight home.
- Cellphone could be boarding pass, too (USA Today)