May 7, 2021. We had already checked in for our flight this morning and arrived at the airport 40 minutes prior to departure for the early morning flight to Dallas from Palm Springs. When we went to check in our bags, the agent told us we were 4 minutes too late to board our scheduled flight and she re-ticketed us to get on a later flight which meant that we missed our meeting in Dallas. We were floored. and perplexed. Stunned. We did not know of this American airlines rule and I cannot find it on American's website or on the internet. We would like an apology from American Airlines and specifically from that ticket agent.