As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
KHUF - NOXIOUS SMELL IN COCKPIT, UNABLE TO LOCALIZE OR DETERMINE ORIGIN. SELECTIVELY ELIMINATED COCKPIT LIGHTING, TC'S AND AVIONICS WITH NO APPRECIABLE CHANGE. RAN ENGINES AND PRESSURIZED AIRCRAFT. ATTEMPTED NUMEROUS ELECTRICAL AND ENGINE BLEED CONFIGURATIONS. COULD NOT DUPLICATE SMELL IN COCKPIT. (X)