Tha majority of Zone games will have modified planes blocked.  Unless the only change to the plane you are flying is the textures then the zone software and CFS1 will detect the plane as a "Mod" and prevent you from flying it.

As with all walks of life the zone has plenty of cheats who like to arm their hurrican with twenty five 50mm cannon and jet engines and then claim that they are the best fighter pilot on the net.  The mods off facility prevents this from occuring.

If you wish to combat test downloaded aircraft I suggest hosting your own game and clearly marking it as mods enabled.

Another method is to join and fly with a reputable squadron, they need to use bombers so often their games will be mod enabled and thus allow you to fly a variety of dodgy planes.

I hope this helps.

Will

_83_Maj_Wilf