As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT T557/22 LIGHT SMOKE AND FUMES IN AIRCRAFT AT FL280. IAW CHECKLIST RECIRCULATION FANS WERE TURNED OFF. SMOKE AND FUMES DISSIPATED. INSPECTED FANS AND FOUND NOISY BEARING IN FAN ALONG WITH ODOR. REPLACED RECIRCULATION FAN. SYSTEM GROUND CHECKED NORMAL OPERATION.--CLOSED--