As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIT-SDF - FLT 1805 - AFTER REACHING CRUISE ALTITUDE, THE LEFT MAIN GEAR RED UNSAFE ILLUMINATED. THE AIRCRAFT RETURNED TO THE FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE LEFT GEAR UPLATCH SENSOR. SEVERAL GEAR RETRACTIONS WERE COMPLETED AND ALL INDICATIONS WER NORMAL. (M)