As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3401 - ATB - PERFORMED AN AIR TURN BACK DUE TO ODOR/FUME IN THE CABIN. CORRECTIVE ACTION: INSPECTED BOTH ENGINES AND APU, NO VISIBLE LEAKS. PERFORMED BORO INSPECTION OF #1 AND #2 ENGINE IP AND HP COMPRESSORS, NO FINDINGS. COMPLIED WITH PACK BURN AND REPLACED CABIN RECIRC FILTERS AND PLACED A/C BACK IN SERVICE. (5868450)