Originally Posted by AAaLot
Was my request reasonable…force them to take people out of the airplane and let us board?
Actually, that is unreasonable, IMHO. No way that could happen in 5 minutes, the whole plane would have been held up. They probably tried to hold off as long as possible before assigning your seats, but when you weren't there 10 minutes before departure, they gave them away. At that point, it's too late. And you probably have no idea who ended up taking your seats. Could have been a few EXPs who had misconnected and were trying to get on standby, for all you know.
What should I do if something like this happens in the future?
My advice would be to make sure, before accepting the alternate routing proposed, that there is enough connecting time. You say the NW flight was on time. So how much connection time did the schedule allow? I wouldn't have accepted anything less than an hour, unless it was the ONLY option. Usually, if they need to re-route you, they'll work with you to find an amenable solution.
Sorry I can't give you more advice as how to deal with the problem that actually happened.