Originally Posted by
notquiteaff
I wonder if TSA at airports where they no longer use boarding passes would let you through with just an ID. Does their system know if you have checked in, or just that you have a ticket? At larger airport, perhaps that would let you get checked in at a service counter or at the gate if there is a long line at the checkin counter. All, of course, only if you don’t have to check bags. At my little airport that isn’t going to work because the checkin counter staff also staffs the departure gate and only arrives there when the checkin window has closed.
I don't think TSA knows if you've checked in or not - all they get is the airline submissions to Secure Flight.
I've occasionally had 2+ PNRs with different airlines departing on the same day out of the same airport, but I was only checked in for one of them. I was asked at the TSA document check which flight I was taking. I also had a time where I was checked in for a flight, but I canceled and rebooked onto another airline. Despite me only having one active PNR, TSA still asked me which flight I was taking.