And the seniority system tends to bias that as well. IOE excepted, the senior CAs tend to fly with the senior FOs because they both tend to get awarded the better schedules. But those FOs are also the best paid and with the best QOL, hence the most to lose stepping back to $100K and a crashpad in EWR or LAX. And even if it would be a faster NB upgrade sometimes, they’d still be junior to thousands of pilots and on reserve in EWR or LAX even longer.

Giving up a lineholder slot anywhere has costs. Giving up a senior lineholder slot at NK - while it will pay off in the long run (at least if you are young enough) - is more difficult. I don’t think we actually lose many senior FOs or lineholding CAs. The bulk of the attrition seems to come in the first 1-2 years.