It never occurred to me to wonder who or what cuts those soul crushing pre-packaged sandwiches that I always find myself eating at an airport, but now I know: it's one of these magic machines. The cutting arm seeks out whole sandwiches and positions its slicer perfectly with ultrasound to deliver the optimal cut.
The general gist (which I just read as sorcery):
Our intelligent robotic cutter integrates advanced motion control, ultrasonics and vision technology, provides the latest in cutting sandwiches and wraps 'on-the-fly' with high accuracy and speed. The system is able to recognise the exact position of the products on the conveyor — regardless of orientation — and communicates this information to the motion control system. This allows the cutting blade to be positioned accurately and a perfect cut to be achieved — all without stopping the conveyor.
So you can put the sandwich any which way and the cutting machine will orient itself as necessary. The video below shows all the things an "intelligent ultrasonic sandwich slicer" can do: