An anonymous reader has posted the following system for streamlining the check-in process at the airport.
Inside the terminal, you proceed along a queue line to the counter as usual. Here, you check in and surrender any checked bags you may have. The bags get the standard destination tag that also has a "match-me" barcode on it. The bags go on a belt, through a scanner and are sealed with a set of tamper-proof straps on which the same barcode is printed before being sent to the staging area (the system is identical to how UPS/FedEx/USPS scan parcels, but with the scan-and-strap step added in). Once the bag is strapped, the check-in agent gets an electronic all-clear and you can move on. You get a magnetically encoded gate pass that has the same "match-me" identifier associated to it, as well as boarding pass (if it wasn't printed beforehand).
Now it is off to the Security checkpoint and, because it is right after the check-in point, congestion is removed as the flow through matches that of the check-in area. Meanwhile, the high-res bag scan images are computer screened. Anything suspicious is forwarded to a human for review. All the human sees is the "match-me" code. If a manual inspection is required, the reviewer hits a button to divert the bag for inspection and also flags the matching gate pass. You swipe your gate pass at the checkpoint, show your ID, and go through the routine you normally do in this area.
On the other side of the checkpoint are lounges, shops, and so forth. Finally, it is off to the boarding lounge, which you enter and exit (if you want to go to a shop or something else) by swiping the gate pass. When you board, you drop it in a slot. This system not only scans it, but also lets the airline know you are on the plane.
As your gate-pass is scanned, the system looks to see if the "match-me" has been tagged in any way. If it has, it allows security to get hold of you should a manual bag inspection be necessary, as it cannot happen till you are accounted for. It also lets the airline know you're at the gate and on the plane you're supposed to be on (no more flights to Springfield, MO when you intend to go to Springfield, MA *grin*) because it will let you know.
As for the cards: They're erased, sterilized (necessary in this day and age), and sent back to the check-in area for re-use. If the system fails entirely, traditional manual screens go into effect. Passengers who misplace the gate-pass have to undergo manual verification screening.
Because documents are still verified at the security checkpoint, hand-offs become difficult since the travel record is attached to the "match-me" code. These are but some of the built-in redundancies. It sounds complex, but it is really a smooth, self-contained system.