FSO isn't about chess pieces.... At the beginning of each scenario, the CO of each squad chooses Axis or Allies and flies that particular side for the duration. It's not exactly like the MA where you fly for a chess piece.
So, if your CO has chosen Allies, say for the Tunisia scenario, you'll probably be relegated to Hurris or something... If Axis, he can request the 262 rides, but they're usually in high demand for obvious reasons.
Hope this helps