Originally Posted by
dakuda
My phone has a fingerprint sensor (Nexus 5X) and when you reboot it, it still requires the PIN for the first login. You can also have it ask for a PIN before it boots at all. Since I generally turn my phone off when I fly, this seems to 'fix' the fingerprint part of a search. I've never had that happen, but it might be something to keep in mind as well.
This is true for the iPhone as well.
You can also choose to have an alphanumeric passcode so it's harder to brute force. A 4 digit PIN only has 1000 possibilities - a computer can try all of them in a few seconds. The iPhone has a "wipe after 10 tries" setting, but they can back up your phone and then try 10 tries on millions of virtual images of your phone in parallel.
I'd recommend coming up with a
passphrase that you can memorize without writing it down.
Hypothetically you can carry a dumbphone, but it's contents won't be encrypted at all and any calls made are in the clear.