Herbie you should use this program call ACman. It will allow you to use up to eighteen hangars. Its a great program that will keep from having this problem happeing again.
My advice for you is for you to make a backup folder of the original stock planes and pace them on each new folder you create so when activate a new folder the progarm will run.
Other will wise it will not function. The original stock planes must bee place in every new Hangar you use.
Now can use over one thousand planes for different Theaters and or what ever you would like to use them for.
Here is the Web you can use to download this fantastic program.
1.
http://www.mnwright.btinternet.co.uk/good luck and I hope I have been helpful.
James007