My bad, I was kinda tired and sorta cranky. Anyways, the P-39 isn't really that great of a plane. The design was prone to crazy stalling and it was sorta underpowered in its early years. Now the P-63(although it looks just like the 39) is a completely different plane. Most of it's parts weren't even swappable with the 39's. It had a powerful engine and a great armament, had almost no design flaws(it still stalled like crazy like the 39), and we need this plane so we have more russian planes. There we go.