Hello,
All new aircraft purchased by an airline will bear a registration number of the country in which the airline set up it's first hub.
My first hub is at Paris CDG, so although my airline also has hubs in Beijing, Bangkok, Chicago or Vienna, all my airline's aircraft are registered with a French number type F-ABCD.
I think it would be a good feature if we could select which country we could register each new aircraft in. It would be nice to see OE-ABC flying out of Vienna, and HS-ABC taking off out of Bangkok Suvarnabhumi.
Ciao.