Hi airhap, judging by your 7 posts, I guess you haven't flown Aces High that long.
I myself am also a newbie with about two months of online flying under my belt.
I fly for Knights at Euro Times and usually experience the same 101 Bishops, 49 Knights and 51 Rooks deal night after night.
Before I put up my own suggestions to fix the unbalancing, I'd like to thank the seasoned "1000+ posts" guys on this forum for simply calling airhap a whiner and leaving it at that.
That really helped...
Now for my suggestions:
1.) Those who log on to Aces High for the first time, are put into the team with the fewest numbers at that time.
2.) When you log on, you will be asked to join the team with the fewest numbers. Should you agree to do so, you will recieve some sort of reward (perk points, or a free ride in a perk plane etc).
Those are things HTC can do, now on to something that is way harder...
Things YOU can do:
1.) If your Country constantly has the numbers advantage when you log on (time-zone specific), simply switch sides to the team with the fewest numbers.
Note: concerning "friends" and the "I fly for country X because I've always flown for them/the others suck" argument
a.) all countries are the same
b.) you'll find new friends in any country
c.) ask your friends to come along with you and help change the imbalance together
2.) Squads: Analyze the Arena-numbers when your squad, or most of them, usually fly - if your squad is on the team which has the numbers more often than not when online - switch sides.
3.) Countries: if your combined numbers are equal/lower than those of the third country stop fightig each other and fight the other country together.