Originally Posted by
CrazyJ82
I thought I had read here on FT that there can be issues sometimes with ATC when new routes start -- the authorities can weigh in on flight numbering to avoid similar numbers on different carriers operating in the same airports at the same time. No idea if that would explain some of the exceptions you point out.
Correct, authorities will review them and will discourage numbers that are similar, like (hypothetically) CX899 with CI899, usually they will do their best to ensure enough diversities. Thought a major airport like JFK I would imagine it will be very hard.