You need 1 crew per flight, but really 2 crews per day per plane. Pilots work about half the days, so 4 crews per plane. That gets you to 8 pilots per plane,

You need 1 crew per flight, but really 2 crews per day per plane. Pilots work about half the days, so 4 crews per plane. That gets you to 8 pilots per plane, which is roughly 6k pilots without redundancy or pilots working very limited segments.