The MCAT system has changed such that registrants will be notified via email if a date becomes available. You must register to be notified when a space becomes available in your preferred location on a specific date. Previously, registrants had to continually check the system to see if a spot opened up. The space will not be held for you since others will be notified concurrently—but this is an improvement over having to check the system for vacancies. The MCAT Notification Appointment Request system will be a big help to applicants.
–Liza Thompson, Expert Medical School Admissions Consulting