You know what they used to call 50-100 seat jet airliners before the "regional jet" was introduced?

Mainline.

DC9, Bac1-11, Fokker 28, Fokker 100, BAe 146, 737-200.

All good paying MAINLINE jobs with MAINLINE benefits, and MAINLINE retirement.

Choosing to call an airplane "regional" in order to pay employees less was genius by management and the biggest failure in the history of ALPA.