The following immigrant petitions in the 2nd and 3rd preference categories must be supported by an approved alien labor certification from the U.S. Department of Labor: Advanced Degree Professionals (not seeking a National Interest Waiver): Skilled Workers; Professionals; and Other Workers. Their priority date is determined by the date an approved alien labor certification was filed with the U.S. Department of Labor. The following immigrant petitions in the 2nd and 3rd preference categories must include a completed application for alien labor certification which is deemed pre-certified by the U.S. Department of Labor: Schedule A workers (RNs and Physical Therapists) and Aliens of Exceptional Ability. Their priority date is determined by the date their immigrant visa petition is filed with USCIS.