Originally Posted by Curving River

I only say this as someone who has flown nearly 5 million BIS miles over the past two decades: while you may not feel that mentioning a lawsuit or the importance of “contract of carriage” is a threat of legal action, most customer service facing employees will take that as a sign you intend to pursue a course of action that will make their life more difficult. The moment you do this, even if you have the most honest of intentions, you’ve likely lost any chance of winning them to your side and securing their assistance.

Based on the timing you’ve provided, I would guess the gate was closed 5-10 minutes early. It too frustrates me that AA does this (and they shouldn’t) but at that point the important thing to determine is what they’re required to/likely to give you for the misconnect - and what you personally feel you’re owed. Then your obligation as a good human being is to find a way to be OK with the delta between the latter and the former and not take it out on airline employees who are powerless to change said difference.

Hopefully with further information from yourself we can provide some advice that will help you move past this bit of bad luck without any further angst caused for yourself.