As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:N/A AT TOP OF CLIMB (FL380) STARTED SMELLING A STRONG ODOR LIKE BURNT CARDBOARD IN THE COCKPIT. RT PACK WAS ON LT PACK WAS OFF. NO VISIBLE SMOKE DETECTED. WE WENT ON OXYGEN. WE SWITCHED OPERATING PACKS AND ODOR WENT AWAY IN A FEW MINUTES. RAN AIRCRAFT ENGINES PER 21-00-01-301 PARA 1H OF FIM. NO FUMES OR SMELLS NOTED. AIRCRAFT OK FOR SERVICE.