As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DCA - FLT 4318 - WHILE EN ROUTE TO BOS, CREW NOTICED SMOKE IN THE COCKPIT. CREW FOLLOWED EMERGENCY PROCEDURES AND DIVERTED TO BWI. AIRCRAFT LANDED WITHOUT INCIDENT. MAIINTENANCE FOUND COCKPIT LIGHTING POWER SUPPLY AT FAULT. POWER SUPPLY REPLACED AND AIRCRAFT RETURNED TO SERVICE. (X)