When I was with 403 RCAF Squadron, in Calgary, during the sixties, we had a War Two Mustang pilot, Freddie Clarke. He was the first to be shot down in the type. He ditched in the Channel and received a terrible gash on his face from collision with the gun sight. The radiator scoop turned him into an instant submarine.
His number two shot down the FW-190 that hammered Clarke, becoming the first Mustang kill of the war. If I remember correctly, Clarke's number two was an American with the RCAF.
So, within a minute the P-51 saw its firs combat loss and victory in the same engagement.