if you get stuck in the lav because the passengers started boarding while you were peeing...you might be in a regional jet...

if it slows down in the descent...you might be in a regional jet....

if none of the mainline guys say "hi" back to you in the terminal...or even your own captain...you might be in a regional jet...

if three FO's are in the crew room raving about their first approach ever to mins that morning...that was a result of a regional jet...

if you've smashed your head, shoulder, hip, knee and feet into at least 45 different objects/protrusions...you might be in a regional jet...

if in flight the sun shade snaps down and you throw on the oxygen mask before you realized what happened...you might be in a regional jet...

if the FO comes back to the cockpit and claims something is wrong because the aileron is jammed and won't move...it might be a regional jet...