Date: 202202
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: B777-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked; Cruise
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Troubleshooting; Workload
Second reporter function: Flight Attendant (On Duty)
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
When detected: In-flight; Taxi; Aircraft In Service At Gate
Result: Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Upon arrival to the plane in ZZZ; a couple of the flight attendants and the first officer; informed me that there had been an unpleasant smell like cleaning solution or a dead animal on the plane but that it had dissipated.  I asked if they were sure it was not a electrical or dirty sock smell (indicative of burned oil getting in the packs)  They assured me it was not.  The smell did not reoccur until in the air: Near the top of climb or just after leveling off; we got a SMOKE CREW REST F/D EICAS caution message.  As this EICAS caution does not have an enunciated checklist and there was no evidence of fire or smoke. I contacted the flight attendants and asked that they check the crew rest area and we began the Smoke; Fire or Fumes checklist.  Moments later; the EICAS caution message disappeared.  The flight attendants reported that they briefly smelled something like cleaning solution when they opened the crew rest door but that it dissipated almost immediately.  The first officer and I decided we should consult maintenance control through SATCOMM.  Before we connected with the dispatcher; the EICAS message briefly reappeared and disappeared.  The EICAS warning did not reoccur again after the second time.  After considering all the evidence; maintenance advised us that it would be OK to continue the flight.  We asked the flight attendants to contact us immediately if they smelled; felt; or saw anything indicating smoke or fire.  The cruise portion of the flight continued without incident; but we remained attentive to possible alternates should anything more occur.  Just before the top of descent; we received a call from the flight attendant in the back of the aircraft.  We had just received our descent clearance into ZZZ1 and a runway change from the ILS 12 to the RNAV Z 12 which generated discontinuity in the arrival.  (an anomaly) We both needed to be present to straighten this out; so I informed the flight attendant that I had to go to get the plane on the ground.About one minute after clearing the runway and before starting the APU; we received a call from the back of the aircraft from a flight attendant reporting an electrical smell.  (It was quite confusing as a slight majority of the flight attendants were reporting the smell of cleaning solution and this one thought it smelled like electrical.)In light of that description; we asked ground control to send the fire department to meet us at the gate.  (I didn't anticipate an evacuation; but felt it was imperative to get the passengers off the plane as soon as possible to avoid the inhalation of fumes should they have occurred.  This is why we proceeded to the gate and asked the fire department to meet us at the there.  Thinking that the smell couldn't be coming from the APU as it was not running when the smell was reported after landing nor during climb; we started the APU so that we could shut down the engines and emergency deplane at the gate should it be necessary.The fire department didn't find any evidence of fire inside the passenger compartment; the baggage compartment; the exterior or any other part of the plane.  Maintenance came on board and asked us to shut down the APU as they all agreed that it was burned oil or hydraulic fluid they could smell; the passengers and flight attendants were off the plane at that point; so I instructed the cleaners to leave the plane and we shut down the APU and left the plane to the mechanics.  Unfortunately; after I left the plane; I was informed from the Chief Pilot in ZZZ that one of the flight attendants had complained to her supervisor about how the situation was handled.  We had very little time to deal with both calls from the back of the plane as we were task saturated in both cases and our priority was getting the plane where it needed to be.   Apparently; something was wrong with the airplane which allowed the odor of burned oil or hydraulic fluid to intermittently enter the cabin.  It isn't really possible to determine if an odor is a threat from it's characteristics (how it smells). In the future; if there is a smell on an aircraft; I will follow the Aircraft Odor - Ground checklist (which I didn't realize existed.) and make an entry in the Aircraft Maintenance Logbook no matter what the odor smells like.


Second narrative: As we were seated for climb out (approx 15 minutes into the flight); the smoke alarm in the Flight Deck Crew Rest (bunk beds) began to sound. Flight Attendants checked Crew Rest areas; no visible signs of fire or smoke; and reported this info to Captain. However; very strong smell of fumes (smelled like wet; moldy socks) in Flight Deck Crew Rest. This smell was also present throughout the Business Class cabin upon boarding in ZZZ; but became much stronger after takeoff. Smell was not only in Flight Deck Crew Rest; but then began to fill the entire cabin. (Again; no visible smoke; only significant smell of fumes). It dissipated slightly throughout the flight to ZZZ1; however became extremely strong again upon descent and landing. Pax in Business Class began to inquire what the smell was. Fume smell was particularly strong on AC Left. Upon descent/landing; the fume smell was substantially potent. Although I was already wearing a mask; I also held my work scarf over my nose and mouth. My eyes also began to burn. After landing in ZZZ1; firefighters and mechanics boarded. Mechanic stated plane 'smelled like oil' and the plane was removed from service (as far as I know). Unfortunately; the Flight Attendants were rushed to another plane to work a flight to ZZZ2; with minimal concern given to what we had just experienced.


Synopsis: Air Carrier Captain and Flight Attendant reported an intermittent fume event that was unidentifiable by flight crew. After consulting with Maintenance the flight continued to destination where Maintenance was summoned.