This Mercenary Air Squadron: World War II expansion adds 11 new aircraft for your MAS:WWII games, specifically:

Netherlands Fokker D.XXI
Netherlands G.1A
Poland P.11C
Poland P.23B Karas
Poland P.37B Los
Commonwealth A-20 Wirraway
Commonwealth Halifax Mk.I
Commonwealth A-46 Boomerang
Germany Me.323 Gigant
Germany Hs.129B
Germany Me-410A