You are correct. The oldest person in the class is the most senior of that particular class. When I started at CAL, I had 8 people older than me in a class of 11; therefore, those 8 became more senior to me on the overall seniority list. As far as class choices went, there were slots for 4 Newark Airbus A300 SOs (Second Officers), 5 Newark 727 SOs and 2 Honolulu DC-10 SOs. The four most senior guys took the Airbus slots. The next five, me being the bottom of those five, took the 727 seats and the last two were given the DC10 positions as they had no other choices when it got to their seniority. The DC10 positions were in Honolulu and being new nobody wanted to commute that far so they were the last to go. Of the two who were forced to the HNL DC10 position, one quit that first day because of his perception of working that far away from home. As it turns out Honolulu was a pretty good gig as I wound up on a 747 there years later. That is how initial equipment and base selections are made. After that initial selection process you end up competing (bidding) on base and equipment openings just like everybody else on the company seniority list. Your older classmates hired the same day will always be senior to you until they retire or quit. Hope that clarifies the process.