This morning on an Eagle/Express (i.e., regional carrier) flight, one of my traveling companion's bags was taken from her "because it won't fit on the plane", a CRJ900. We were seated together (in first class) and the bag would easily fit under the seat in front of us, so I stepped forward to get it back.

"Sir, the bag's already been taken off the plane. You can't get off the plane to get it back", even though it was still there on the jetbridge, 10 feet from the entrance.

Later, the same flight attendant announced, as usual, "If you don't wish to travel to XYZ, now's the time to deplane."

So...when can you deplane and when can't you? It's not allowed to just reach off the plane to pick up something on the jetbridge?

Thanks.