Originally Posted by
Dr. HFH
Perhaps those particular models weren't selling well.
I don't think so. Each of the model types, especially in the 1:500 scale received several editions (production runs), each with its own registration.
Of course the most popular was the 747-400, with B-HUI, B-HUJ, etc, and even with two editions of the PW-powered plane. But the A330 had many production runs as well.