[ordway]

Have you put the correct entry into the plane_ru properties file as well?

Plane_ru.properties;
P-26 P-26, 1932

Your air ini entry should look like this.

Air.ini;
P-26 air.P_26 1 NOINFO usa01 SUMMER

I had the same problem for hours:

As Triad 773 says: "Extracting the "P-26 Plane" to the MODS folder will not work. You must take out the "P-26" folder within the P-26 Plane folder and place THAT into your MODS folder."