Why don’t some models fly? If you are using the AeroFly Professional without Expansion Pack 1, the reason may be the following one: This problem concerns my Twinjets and flying wings and LEGOS F4U-1A_Corsair: For these models we used the airfoil NACA 0012, which unfortunataly is not part of the AFP without Expansion Pack 1! Therefore the Twinjets have the following problem: the model's pitch changes with elevator up or down but with little effect on its flight path, while the flying wings estimate themselves But You can do something to solve these problems: Open the tmd-file, for example AS_Twinjet_W.tmd with an editor, e. g. Wordpad, and search for the line with the entry NACA 0012. You will find it in the section 'cd Leftwing/' and 'cd Rightwing/' : SectionAirfoil(1) = "NACA 0012" Now change 'NACA 0012' into 'NACA 0015' : SectionAirfoil(1) = "NACA 0015" Then save the file and with the next start everything will be O.K.