This week, British Airways and Subway have both updated their iPhone apps to bring Passbook integration for customers in the UK.
The British Airways app, which was updated on Wednesday, now enables customers to store their boarding passes in their iPhone.
"By mid June we'll be enhancing Passbook boarding passes by adding direct links to them from your iPhone's lock screen as you're ready to fly," BA promises. "This will make it even easier for you to access your boarding pass on the move. We'll send you a message via the app as soon as these are enabled."
Meanwhile, Subway's Subcard App has also been updated to include Passbook integration. Customers' Subcard ID and recent transactions and loyalty card points can be accessed from Passbook.
Both the British Airways app and the Subway Subcard app are available as free downloads from Apple's App Store.
Yesterday, Apple updated its iTunes Festival 2013 app to add Passbook integration too.