Originally Posted by MSPeconomist

If you do OLCI or use a kiosk, you still must show your physical passport to some agent (and have it entered into the system that you have done so, proved by having "DOCS OK" print on a new boarding pass) before boarding an international itinerary. DL doesn't want to risk being fined because a passenger has forgotten a passport or misrepresented the expiration date, etc., after entering the details during self service OLCI or kiosk check in. Everyone normally also at least flashes the passport when boarding international segments as a final check that the passport wasn't lost/forgotten/misplaced in the airport or on some connecting flight.