In the last years of Compass, there was no flow - and even before that there was basically just a “guaranteed interview”. But Delta could have sent the aircraft to Skywest, Republic, or wherever.

Flow became a thing when it was necessary to keep regional FOs and especially CAs from jumping ship - same for the surge in DECs - back when regional aircraft were being parked for want of FOs with enough 121 time to upgrade coupled with losing CAs. But that was a queuing artifact caused by decades of pi$$-poor regional pay, the major early retirements and then the post COVID early rebound of flying. But that temporary dearth and the regional pay boost it caused stimulated an unsustainable increase in the number of new flying schools - especially with the new rules allowing rotary military pilots expedited ATPs.

Eventually like any blip in a supply line, career progression will ultimately be limited by its most limiting factor which for 121 flying has always been major hiring which is a function of retirements plus or minus either growth (think UA) or contraction (think NK).

The pilots at the majors will fight like crazy in their CBAs to avoid any regional expansion. Which means this becomes the limiting factor for career progression:


https://www.fapa.aero/pilot-hiring-history

Which is ultimately limited by retirements and growth (if any) and subject to the usual black swan events of war and economic turmoil, even legislative action (age 67?) or technology (single pilot 121?).

Don’t get me wrong, I love flying, and it can be a great career, but don’t assume recent history (post COVID) represents steady state reality. It doesn’t.