Ok. Here's the deal. Make a fourth country and call them the "Queens."
Now the "Queens" have all free accounts. But they have a very limited plane set. 202's, P-36's, Spit V's, Buffaloe's, TBD Devastator's, etc, etc, etc....
The other three countries, that we have now, have access to all the planes available, until (here's the kicker!) the number of the "Queens" logged on reaches fifty. Then the other three countries emmediately have access to the perk planes. The "Queens" of course do not.
If by some stroke of fortune we are fortious and have one hundred Queens logged on then B-36 bomb load is nuclear capable.
-Westy