Continental Airlines has expanded its paperless boarding pass system to more airports. Passengers who are flying out of Houston, Boston Logan, Newark and Washington Reagan on domestic itineraries can now opt to receive an emailed boarding pass to their cell phone or handheld device. The electronic boarding pass will display passenger and flight information along with a bar code that can be scanned by security officials gate agents.

Northwest Airlines is testing a similar paperless boarding system in Indianapolis for passengers flying on nonstop domestic flights. Users can check in at nwa.com with a PC or mobile handheld device and have their boarding pass sent to their cell phone or PDA. Northwest has future plans to add more cities to its e-Boarding pass system.