What was found
LEFT REAR PASSENGER DOOR OPENED DURING CRUISE FLIGHT. AIRCRAFT WAS SLOWED DOWN TO 25 KTS IN ORDER FOR CREW MEMBER TO ATTEMPT TO CLOSE IT. HE WAS UNABLE TO SLIDE IT CLOSED, AND CONTINUED TO HOLD THE DOOR UNTIL A PRECAUTIONARY LANDING COULD BE MADE. ONCE LANDED AND VIEWED FROM OUTSIDE, THE FORCE OF THE DOOR OPENING IN FLIGHT CAUSED IT TO COME OF THE TRACK. MECHANIC WAS NOTIFIED AND RESPONDED TO THE AIRCRAFT LOCATION. MEHANIC PERFORMED INSPECTION OF DOOR AND REINSTALLED IT ON TRACK PER AMM. VERIFIED DOOR OPENED, CLOSED, LATCHED AND CAUTION LIGHT OPERATED CORRECTLY. NO DEFECTS WERE NOTED. COULD NOT DUPLICATE FAULT.