As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEPARTED DTW, EN ROUTE TO ADS, AFTER ABOUT 5 MINUTES AT FLIGHT LEVEL 390 THE ALTITUDE ALERTER CAME ON. THE FLIGHT CREW FOLLOWED EMERGENCY PROCEDURES AND LANDED AT SUS WITHOUT INCIDENT. INSPECTED AIRCRAFT AND FOUND FLOW CONTROL VALVE HAD GONE BAD. REPLACED FLOW CONTROL VALVE ALL OPERATIONAL CHECKS AND TEST FLIGHT CHECK GOOD. (M)