To add multiple Interrail/Eurail passes to your device, open the ‘My Pass’ tab in the Rail Planner app and tap the orange ‘+’ button in the bottom-right corner. Enter the details for any additional passes, and they will also be stored in the ‘My Pass’ tab.
Each pass needs to be linked to a trip. The easiest way to do this is by duplicating an existing trip:
Go to ‘My Trip’.
Select the trip you wish to duplicate & tap the 3 dots in the top right corner.
Select ‘Duplicate trip’.
Give the duplicated trip a new name.
You can then link each additional pass to one of the duplicated trips.
Remember that you’ll need to activate your journeys separately for each pass.

