I'd like to hear more from someone in the industry about the resolution to this problem. As I understand it, we're trading a small non-zero risk of mistaken identity for the streamlined communication of using four digits rather than five (which carries its own non-zero benefit to safety). This has become a problem because airline consolidation means some of them operate so many flights per day that their limited pool of numbers dictate that they reuse them for either direction.

Could we resolve this by swapping one number for a letter? 26 options instead of 10 raises the pool substantially. Letters A-J indicate inbound, K-Z outbound? Or westbound/eastbound.