Dortmund is one of the biggest shows in Europe that caters for i would say just about every type of modelmaker, not just the normal Planes/Helicopters, Boats, Trucks, Railways.. but also fairground, and all sorts..
by the way, i have been going to Dortmund since the 1980's every year, and will be there this year in Hall 5..
there is also the trade fair in Lipzig, this is more of a toy trade fair, with just one hall for the modelmakers..
a rather large an new trade fair is in Friedrichshafen.. worth a visit..