Nope! Flying already existences in Base. As soon as pilots activate they can build lines!
8-F Activation Of Assignment
8-F-1 A Pilot’s date of “activation” shall be the date he begins in a new Category and is set by:8-F-1-a the beginning of the first segment of his OE in that Category;
or 8-F-1-b the beginning of the first segment of his first trip after training for that Category, if OE is not required;
or 8-F-1-c the first day on which he begins a schedule in that new Category, when no training is required.