It looks like United Airlines (s ual) isn't the only airline that will integrate boarding passes with Apple's(s AAPL) new Passbook feature coming in iOS 6. Both American Airlines (s amr) and Delta Airlines (s dal) are likely on board as well, according to travel industry blog Skift.

Passbook, if you'll recall, is an Apple-created app that can hold digital boarding passes, rail tickets, movie and sporting event tickets, hotel confirmation info, coupons, gift cards and more.