Do I need to worry about being shadow banned after a flight?

Nope. I'm traveling a lot, also intercontinental, and never got banned.

No, don't worry and get a new regional.

As long as you don't open the game mid flight so that no GPS is sent to the servers then you'll be fine. I can see on spoofer channels that they have to wait for at least 2 hours if they are about to fly a 1,000km distance. Lots of them are getting the warning screen everyday.

Edit: Playing PoGO at airports waiting for next flight is fine too. Have fun catchin' em all! ^^

no, a few hours later won't matter in fact it would be silly if they did that. I think the window period for cooldown is like 4 hours from one point to another even if somehow triggered.

I've done it several times without an issue. Even caught a Farfetch'd in Taipei airport! Still my only one.

No worries, I fly a lot and leave mons in every airport I stop over at.

My first account got banned when I travel Singapore-Sydney-Bali for 3 days, with one day per region.
That was still level 28 in September 2016.
And I still remember, every flight time I was resting my account around 5 hours. But why that had banned.