What was found
IN FLIGHT, NR 4 L/E FLAP LIGHT ILLUMINATED. AIRCRAFT RETURNED TO STL AND MADE AN UNEVENTFUL LANDING. REPLACED DOWN PROX SENSOR PER BOEING MM.
As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
IN FLIGHT, NR 4 L/E FLAP LIGHT ILLUMINATED. AIRCRAFT RETURNED TO STL AND MADE AN UNEVENTFUL LANDING. REPLACED DOWN PROX SENSOR PER BOEING MM.