The check-in agent was correct. The GA violated AA's internal procedures (nothing to do with DHS).
Some smaller stations will accept bags after the deadline because they know that it does not take much time for the process to move them from the counter to the aircraft. But, the agent bears the brunt of this if it goes wrong.
AA's rule is clearly stated on its website. For all the bickering, this has been on the website for as long as I can remember. At the same time, the people who keep talking about bag-match are now 14 years behind (it went out in 2003 for domestic).
General acceptance of baggage
Only baggage as defined in the definition section will be accepted for transportation. All baggage is subject to inspection. Checked baggage will be accepted for transportation only on flights on which you are traveling.
AA should only have permitted OP to voluntarily change is flight if it could also move his bag. It is unclear to me that this was even attempted or whether it occurred.
There is a reason for the deadlines. <redacted>
Last edited by JDiver; Feb 14, 2017 at 11:44 am
Reason: Redacted meta and unnecessary characterizations