Rocket,
1. S1 = company business (N/A for non-rev) = FREE
2. S2 = highest non-rev status. Limited number of S2 passes. S2 takes priority over all S3 pass riders; however, seniority prevails compared to other S2 pass riders. S2 = FREE
3. S3 = UNL number. Seniority prevails. S3 = FREE.
4. S3B = parents. FREE but limited number.
4. S2 / S3 is selected at the airport / kiosk.