What was found
THE LOOP ASSEMBLY IN THE UPPER SILL PLATE OF THE FUSELAGE AFT CABIN DOOR BECAME LOOSE, ALLOWING THE UPPER LATCH AT THE TIP OF THE DOOR TO RELEASE DURING CRUISE FLIGHT. THE TOP PORTION OF THE DOOR INCLUDING THE WINDOW, SUBSEQUENTLY BROKE OFF, DENTING THE LT INBD LEADING EDGE STABILATOR SKIN BETWEEN THE 2 MOST INBD RIBS. NO FURTHER DAMAGE WAS NOTED, AND FLIGHT CHARACTERISTICS REMAINED UNAFFECTED. PRIOR TO FLIGHT THE DOOR APPEARED TO BE SECURELY LATCHED.