Kind of surprised to ee so much negativity here. It's nice to see an airline actually enforcing its rules. If you don't like it, fly someone else -- that's what I usually do.

I flew F9 once this year and my backpack what right on the cusp of what was allowed. Well before boarding (when it wasn't busy) I kindly told the gate agent I can make my bag smaller if needed (one of those adjustable backpacks) and she said not to worry about it since I was in stretch seating anyway, but thanked me for asking. I boarded early so I didn't get to see how strictly they enforced bag sizing for the rest of the cabin.

-J.