Originally Posted by DrAlex

If you are not checking bags (but have checked in), this shouldn't be a problem. It's not like TSA does anything to communicate to the airline you are in the secure area. GA might be less willing to do it than a CS rep, but YMMV.

If you have a checked bag, it should/would just take more work. I had a situation last year where I was supposed to connect in SAN, but the inbound was late and I knew I would misconnect. AS put me on a direct DL flight AND got my bags retagged all from inside security at the CS desk. I would think if you have a bag checked and cancel they could just spit out your bag with an arriving flight or maybe one of the baggage agents could retrieve it.