Yes! One subscription is good for all of your devices. Just make sure you are logged in under the same email account on all devices. You can check that in the app's menu > Settings in the Flight Crew View Account section.
"Continue with Google/Apple" login button (potential issues)
If you logged in using one of those "Continue with..." buttons, but aren't sure how to log in on other devices, here are some steps you can follow:
Create a Password:
If you aren't logged in to your Google/Apple account on the other device, you will need to create a password and log in with email/password. You can easily add or update a password in the Settings page in the app.
Apple Anonymous Email:
If your email looks like this in the app: *****@privaterelay.appleid.com, then you are using Apple's Hide My Email feature (it's enabled by default by Apple). read here for more info about how to handle this:
If you still have trouble, please send us an email via the Contact Developer option in the app's menu or at firstname.lastname@example.org