It's all about the slots and the gates. 21 days is far too short for airlines to move equipment into new routes and advertise them.

A cap on the % of slots and gates should be implemented, and the incumbent carriers could override it IF-AND-ONLY-IF no one else wants to bid on and operate the slots/gates. For example, United is not going to bid on Omaha slots and gates if they don't plan to compete with Southwest.

Airlines that are hoarding these should be forced to cough them up if they are not being used.