Originally Posted by jameslon
Elaborate as the theories may be, there is a relatively straghtforward answer, at least for BA flight numbers

I cannot vouch for a mix of bookings on different carriers.
Bookings are sorted cyclically by flight number, BA0xx, BA1xx, BA2xx. For flight numbers preceded by 0, drop the 0. The second digit counts for the sort.
I think post 10 of this thread would not agree with you