You pay the same $10 for 1GB of data post which the bill protection kicks in is free but with slower speeds. Project Fi will look up for any upcoming trips from Gmail flight reservations and will alert you through a banner in the app letting you know if you’ll have Fi coverage. You will also receive a notification in your Project Fi app shortly before the trip allowing you to easily check the cost estimates, your coverage options, and more. These notifications will be enabled by default, but you can turn them off.
If you are already a Project Fi customer, you don’t have to do anything to activate your international coverage since it is part of your phone plan. On the other hand, if you’re willing to join Project Fi for a limited time, you’ll get an $80 Fi service credit with the purchase of any new Fi-friendly phone.