Narrative:

After the jetway was pulled; the purser informed me flight attendants were smelling something unusual near door 3L. I sent the relief pilot back for verification. He; too; smelled it. We informed maintenance. They boarded the aircraft and after troubleshooting they were not able to find the source of the smell. By this time it had dissipated; so we all agreed to depart. After 1 hour in cruise; the smell returned. I immediately contacted maintenance and dispatch via satcom. After troubleshooting with maintenance; we all thought it was a bad sidewall light ballast in economy. Once those lights were shut down; the smell quickly dissipated. Again; we all were in agreement to continue. I was comfortable with this decision because it wasn't a burning smell--simply a hot smell. Also; it was very; very localized and there was no smoke or heat associated with the smell. Several hours later; we were again informed by the flight attendants that the smell had returned. I immediately dialed dispatch and maintenance on the satcom. I was obviously very; very concerned. I decided to go back and smell it for myself. This time; as I approached the area; I smelled a burning smell. It was very strong this time. I immediately returned to the cockpit and informed maintenance and dispatch of this. I immediately informed ATC and diverted to the nearest airport which was approximately 95 miles away. I also requested that the fire equipment be standing by just in case. I had the flight attendants continually monitor the area; especially looking out for smoke. I told them to contact the cockpit at any time prior to touchdown if they saw smoke. Dispatch remained on the satcom until touchdown. SOP was followed. All applicable checklists were performed. We landed uneventfully. The fireman boarded the aircraft as a precaution to ascertain the status of the area in question. They did not find an active fire or 'hot spot.'finally; as an aside; one thing did surprise me during this event. I had the first officer fly greater than 250 KIAS below 10;000 ft because I felt we needed to get on the ground as quickly as possible. I informed ATC of this. What was unusual was that at approximately 20 NM from the field; approach control had us slow to 220 KIAS as if he needed this to maintain spacing with another aircraft. Since there still wasn't smoke in the cabin; I decided to accept this clearance. What I find strange; however; is that I was under the impression that [distressed] aircraft had priority and all other traffic was cleared out of the way. That was clearly not the case here. Obviously; had we been on fire; I would not have accepted this speed restriction.

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Original NASA ASRS Text

Title: B777 Captain reported a strange smell near door 3L prior to engine start and Maintenance evaluated with nothing identified. The smell returned several times during the flight; and when the odor returned as a burning smell; the flight diverted.

Narrative: After the jetway was pulled; the Purser informed me flight attendants were smelling something unusual near door 3L. I sent the relief pilot back for verification. He; too; smelled it. We informed maintenance. They boarded the aircraft and after troubleshooting they were not able to find the source of the smell. By this time it had dissipated; so we all agreed to depart. After 1 hour in cruise; the smell returned. I immediately contacted maintenance and dispatch via SATCOM. After troubleshooting with maintenance; we all thought it was a bad sidewall light ballast in economy. Once those lights were shut down; the smell quickly dissipated. Again; we all were in agreement to continue. I was comfortable with this decision because it wasn't a burning smell--simply a hot smell. Also; it was very; very localized and there was no smoke or heat associated with the smell. Several hours later; we were again informed by the flight attendants that the smell had returned. I immediately dialed dispatch and maintenance on the SATCOM. I was obviously very; very concerned. I decided to go back and smell it for myself. This time; as I approached the area; I smelled a burning smell. It was very strong this time. I immediately returned to the cockpit and informed maintenance and dispatch of this. I immediately informed ATC and diverted to the nearest airport which was approximately 95 miles away. I also requested that the fire equipment be standing by just in case. I had the flight attendants continually monitor the area; especially looking out for smoke. I told them to contact the cockpit at any time prior to touchdown if they saw smoke. Dispatch remained on the SATCOM until touchdown. SOP was followed. All applicable checklists were performed. We landed uneventfully. The fireman boarded the aircraft as a precaution to ascertain the status of the area in question. They did not find an active fire or 'hot spot.'Finally; as an aside; one thing did surprise me during this event. I had the first officer fly greater than 250 KIAS below 10;000 ft because I felt we needed to get on the ground as quickly as possible. I informed ATC of this. What was unusual was that at approximately 20 NM from the field; Approach Control had us slow to 220 KIAS as if he needed this to maintain spacing with another aircraft. Since there still wasn't smoke in the cabin; I decided to accept this clearance. What I find strange; however; is that I was under the impression that [distressed] aircraft had priority and all other traffic was cleared out of the way. That was clearly not the case here. Obviously; had we been on fire; I would not have accepted this speed restriction.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.