Booking ID’s. If/when do they ever get duplicated?
 

I was airside and my SN flight was cancelled and rebooked on AF. I was able to go straight on the AF website and check in with my name, flight # and the exact same six digit booking ID. Simple, and I’m actually a little impressed that it was so slick.

AF had clearly had my booking ID transferred over, but is it possible for them to have already issued the same ID for one of their bookings? And what if they had?

And generally, worldwide, do are there ever two identical ID’s in circulation at the same time? And has it ever caused a problem?

I get that the chances are 1 in 2.17bn of two ID’s matching, but if the total number of pax flying per year is 4bn or so then doesn’t this become statistically highly likely?