The millennial bombers were headed to LAX when they were arrested coming off a ferry from Canada. So we have known since then that the check in or security mob scene at International Airports has been a target. I stopped using LAX for my flights for just that reason.
I have two thoughts: One, they might do it at a smaller airport where security may be more limited (MLI/ Moline,IL/SBA -Santa Barbara,CA are good examples) or two, a larger one where it would cause more damage/deaths such as JFK or LAX.