[gruez]

>but some applications do require this level of identity proofing (scanning your passport in an airline mobile app to book an international flight comes to mind).

I never had to do this when booking a flight. The max I had to do was provide my personal info (name, birthday, passport number). If they asked for a passport scan and a selfie I would have noped out.

[legerdemain]

Kayak asks for ID photos, even for domestic flights.

[Someone1234]

But the underlying airlines don't, so just find the flights on Kayak then book direct bypassing this invasive measure.

[xyzzy21]

Never used Kayak but thanks for the tip: I NEVER will use Kayak!