Passbook hasn’t gone public yet, but that hasn’t stopped several companies from pledging their support. Most of the major airlines already appear to be on board with the service, and now it looks like theme parks are in as well.

Accesso, one of the largest providers of theme park and attraction tickets in North America, has just announced that it will be one of the first travel industry suppliers to adapt its ticketing platform to work with Passbook

From the company’s press release (via AppAdvice):

accesso, a leading provider of attraction ticketing, will be one of the first travel industry suppliers to adapt its ticketing platform to support Passbook, a new mobile device feature in Apple’s soon-to-be released iOS6 operating system…

…With accesso’s new enhancement, consumers will be able to import ticket purchases from attractions including 11 Cedar Fair Entertainment theme parks and the Columbus Zoo and Aquarium directly into their Passbook app.”

This is great news both for Apple, and for folks pulling for the digital pass service to thrive. As we’ve said before, Passbook’s success depends on the amount of support it garners from major businesses. It has to be ubiquitous.

And despite backing from major airlines and now accesso, the service still has a long ways to go. Support from companies like Fandango, and TicketMaster, for example, are still musts, as are all major retailers and restaurants.

It’ll be interesting to see if Apple announces any new partners this Wednesday, when it is expected to unveil its new iPhone and announce the public release of iOS 6. Remember to tune in to iDB for full event coverage.