If you have purchased FlightUpdate and also purchased the upgrade to the "Pro" features but find that the "Pro" features are missing, you can easily resolve this.
Because the indication that you upgraded to the "Pro" features are stored deep in the device, you should not lose the upgrade. But sometimes, if you restore the device or erase the device, the indication that you upgraded is lost. You will need to do this also if you purchase a new device.
Do NOT go back to the App Store and purchase the Pro version. Doing this will cause you to be charged for a brand new product. This is the case because Flight Update and Flight Update Pro are two distinct apps on the App Store.
To get back the upgrade for Flight Update, simply launch Flight Update and open the Prefs screen. Tap the "Upgrade to Pro" and go through the process of purchasing the upgrade again (this by the way is called an In-App Purchase). You will absolutely NOT be charged again as long as you use the same iTunes account that you used when you originally purchased the upgrade. iTunes will remember that you own it and ask if you would like to purchase it again.