Editing a user you have the option to remove a user. It is important to know that removing a user doesn't delete their flight records, rather it removes them from your ATP. Their account will be locked unless they have an active subscription.
If you remove the aviator and need to bring him or her back to your ATP please contact us.
Now that you only have 9 people and you are authorized 10 you can now add an aviator to your ATP.