Widebody Transport
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Issued New Clearance; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification
Aircraft
On the arrival; descending through about FL180; the Captain and I could see and smell smoke in the cockpit. It was definitely noticeable but not strong enough at that point to cause physiological issues. There were no audible or visual detector indications of fire or smoke in the cargo areas; just the sight and smell of smoke in the cockpit. We immediately donned our oxygen masks and notified the jumpseater in the courier area to do the same. As the Captain continued to fly the airplane; he [advised ATC] and requested priority landing. I ran the Smoke/Fire/Fumes QRH procedure and within a few minutes; the smoke dissipated. We left the oxygen masks on and continued for an immediate landing; just in case the smoke returned. We landed uneventfully and taxied to the gate. Fire personnel boarded the airplane to gather information about the event.It was not clear to us what caused the smoke. Maintenance asked if it smelled like an electrical fire; and neither of us thought so. To the Captain; it was more of a petroleum-based smell. The airplane came out of major maintenance recently.
Widebody cargo aircraft First Officer reported smoke of unknown origin in the cockpit shortly before landing.