It was just a few months ago that Apple added Passbook to iOS 6, providing an easy way to tuck away virtual ticket stubs and your affinity cards in an iPhone or iPad. Mobile airline boarding passes were introduced quickly by United Airlines, American Airlines, and Lufthansa, and now a total of 10 airlines support the ability to store your boarding pass in Passbook.
In addition to the three pioneers, Air Canada, ANA (domestic flights only), Malaysian Airlines, Porter Airlines, Qantas, Turkish Airlines and Virgin Australia are now Passbook-friendly. British Airways and Delta are supposed to be adding support soon.
I had a chance to use Passbook in October on United Airlines and found it to be simple and convenient to use. Passbook works very well in concert with the free United Airlines app, converting an online check-in into a Passbook boarding pass with a tap. Judging from the number of iPhones I saw being scanned at the gate, Passbook is extremely popular with the flying public.