Fill all plane slots as early as possible. Secure all available plane slot as soon as possible without waiting for missions to include it on your list. Do not worry if it is included later, as it will automatically be marked as completed. Naturally, this requires a lot of money. The more planes you are operating, the more money and experience points you will earn. Assign different paint colors to your planes. This will help you identify your planes and manage them easier. Do not use the auto-flight feature, unless absolutely needed during the single player campaign. Manual control has much better results than AI control.