Originally Posted by
EvilDoctorK
Without knowing the detail I always thought it was an East/Westbound thing .. it's not just BA .. but on Transatlantic anyway most airlines seem to follow the convention that Eastbound flight are even numbered and Westbound odd numbered
I believe it's a BOAC vs BEA thing.
BEA numbered outbound from London as even numbered flights.
BOAC numbered outbound from London as odd numbered flights.
The practice has continued to this day.