What was found
AFTER TAKEOFF, LEFT MAIN GEAR RED LIGHT REMAINED ILLUMINATED. RECYCLED GEAR AND LIGHT EXTINGUISHED. AIRCRAFT LANDED WITHOUT INCIDENT. INSPECTED, TIGHTENED RED LIGHT BASE, AND OPERATION CHECKED PER BOEING M/M. ON NEXT FLIGHT EXPERIENCED RED LIGHT FLICKERING IN FLIGHT. REPLACED LEFT MAIN GEAR UPLOCK SENSOR PER BOEING M/M.