Originally Posted by Clue32

Not sure how you deduced that. Applicants are asked for their fleet preference in the HR interview. The hiring team will consider that with the applicants experience level in offering a FO position and fleet. Low experience will generally lead to a 737 offer. 1500 hours in C-5s or KC-10s and a the door to a 747 probably is still open.

Seniority and fleet vacancy, after completing a 24 month new hire seat lock, gets a FO into a different aircraft.