The British Airways app is a straightforward implementation of Apple's digital repository, with basic support for boarding pass storage. All other functions, like seat changes and push notifications, are taken care of by the company's official app.
The app also lacks integration with Passbook's geolocation services, which in the case of an airline app would bring up a user's boarding pass upon arriving at the airport. The airline said such service would come in an update expected by mid June.
British Airways for iOS comes in at 6.3MB and can be downloaded for free from the App Store.
As for Subway, the restaurant chain is now linking its Subcard loyalty point card app to Apple's service, allowing users to check recent transactions and points balance directly from Passbook. Once customers accumulate enough points, they can redeem them for a free sub sandwich. The new support is limited to the UK.
Subway's Subcard app is a 1.9MB free download from the App Store.
The new additions comes after Alaska Airlines announced adoption of Passbook last week, taking advantage of the service's advanced features like dynamic updates for seat assignments and geolocation integration.