Space for carry-on luggage is limited. If you board last, there is a high possibility that the airline will check-in your carry-on luggage instead. This will cause you a delay since now you need to wait in the baggage claim area after arrival. Had you boarded just 5mins prior, someone else might have to wait 30mins in baggage claim instead of you.
Ever have this happen? It doesn't happen this way.
They have special space for "checked carryon." they ticket it with a special ticket and put it in a SEPARATE part of the plane. When you unload the flight attendants get the "checked carryon" and put it next to the door, then you grab it on your way out.
I sat on the front of a small plane before and there was no space for carryon at all on that seat. There was no seat in front to put it under, and the overheads on that seat had a bunch of flight attendant stuff in them. Being the first on the plane wouldn't have enabled me to avoid the "checked carryon."
This is by no means how it commonly works.
Some planes will "gate check" your carryon, but most of the time that last-minute checked luggage gets checked through to your final destination.
And for the other comment above, the plane certainly WILL leave without you.
This weekend, my partner had her backpacked gate-checked, but it didn't go to the separate part of the plane. It became checked luggage, which then failed to come off the plane and landed in another airport. Fun times having a carryon lost on you.
Uh, excuse me - what? If the overhead compartments for carry-on baggage is full - you got plenty of space under the seat in front of you.
The only exception is really if you're by the emergency exits - then you're not allowed to have anything that could obstruct or confuse people when they make their way to the emergency exit.
Well, that came out silly in hindsight - of course there are more options than the overhead compartment and under the chair in front of you.
What I was trying to say is that I've found it unusual that I've not been able to put my carry-on baggage under the chair in front of me and I have not noticed the flight crew having to handle any other options than the two above.
