Ahead of next week's launch of iOS 6, three more major companies have officially added their support for Apple's new Passbook feature for iPhone: Delta Airlines, Ticketmaster, and Starwood Hotels, owner of Sheraton.

The three companies were not shown in previous promotional material for Passbook, but appeared in the application in an onstage demo at Apple's iPhone 5 unveiling on Wednesday. iOS chief Scott Forstall revealed their participation as he demonstrated how the new Passbook application in iOS 6 works.

"Passbook is the best way to collect all of your passes in one place," Forstall said, showing off movie tickets from Fandango, a Delta boarding pass, a coupon for Target, a store card with remaining balance from Starbucks, and a concert ticket from Ticketmaster.

Delta's involvement with Passbook confirms a rumor from last week that suggested the airline company would join American Airlines and United Airlines in supporting the new digital wallet and ticketing service of iOS 6. But Wednesday's presentation was the first word of Ticketmaster and Starwood also participating.

When Passbook was unveiled in June, the application was also shown to support Amtrak, W Hotels, United Airlines, and the Apple Store. A full list of companies that support Passbook has not yet been detailed.

In his demonstration, Forstall accessed a ticket for a baseball game he had already attended. By deleting the ticket, an animation played showing the digital ticket running through a paper shredder, which drew applause from the audience at the Yerba Buena Center for the Arts in San Francisco.

"One of the really cool things about Passbook is it integrates with the lock screen," Forstall explained. So if I have my phone locked and in my pocket and I get to the airport, my boarding pass already appears on the lock screen, I slide across, it brings up my boarding pass, I scan it and get on the plane. It's that simple."