Originally Posted by
Finland Station
There used to be a reasonably coherent flight numbering scheme used by BA s/h up to about 5 years ago (the remnants of which remain visible). Then the wheels fell off. The most egregious breach of the convention was to use a flight number beginning 3 for flights to/from AMM. Historically BA3xx were flights to/from France.
You might want to check the flight numbers to and from BRU, which date back considerably longer than 5 years!