Can't imagine how this could possibly go wrong. Definitely not false results due to changes in skin colour, hair colour, etc.

I'm really really not in favour of the trend to biometricize everything because I just do not think our current methods are accurate enough.

> changes in skin colour

I can already envision the long and growing queue of badly angered, badly sunburned tourists leaving any number of places in the Caribbean

Something over twenty years ago, I met my father and stepmother at Dulles. He had adhesive tape all over his nose from a fall on vacation. I wonder how that would have worked.

The same way TSA verifies your face against your physical identity credential: a margin of error, with additional proofing performed if your face isn’t enough (you can fly without a government ID, for example, if you show up a bit earlier at the TSA checkpoint for additional screening/proofing).

https://www.tsa.gov/travel/security-screening/identification (control-f Forgot Your ID?)

Or we could just use the existing technology, which is more reliable, simpler, cheaper, requires less expensive gear, is easier to set up and maintain, can be explained to the layperson in 2-3 sentences, and offers far less chance for bad actors to abuse it.

Just because something is more complex, doesn't make it better.

it's the norm in China: bus, train, you name it. Social Credit Score