Narrative:

After level off at FL340 and approximately 1+30 hours into the flight the flight attendant (F/a) in the aft galley called the flight deck and reported to the captain that the smoke detector alarm in the aircraft left aft lavatory had been activated (was sounding off). Normally; pilot thought where there is smoke there is the possibility of fire. So; the captain transferred control of the aircraft navigation and radios to me while she continued to question the F/a on the situation; prepared to run the appropriate QRH checklist; talk to all appropriate individuals and agencies; and get the aircraft on the ground safely and expeditiously. Mind you this is all happening simultaneously.during the subsequent questioning of the F/a the captain asked; 'did you or do you see fire now or any indications of fire?' the F/a response was no. In addition; the captain asked; 'is there still smoke; or has it dissipated?' F/a response was the smoke had completely dissipated and the smoke detector alarm is no longer sounding and had been reset.subsequently; the captain informed me of the conversation with the F/a and again that there was no fire; indications of fire; the smoke had completely dissipated; the smoke detector alarm was no longer sounding; and had been reset. Therefore; the captain made the decision; which I fully supported; that no diversion was necessary. However; we complied with the 'two person in the cockpit rule'; and I went to the aft galley/lavatories to check things out as an added precaution.I asked the F/a what happened? The F/a stated; that passenger hot meals were being cooked for the first service. For some unknown reason one of the aft galley oven doors was left open and started smoking. In addition; the aircraft left aft lavatory door was also open. The F/a believed the combination of the oven door left open; the oven smoke; and heat somehow triggered the lavatory smoke detector alarm to sound.I investigated the lavatory in question and found no fire; indications of fire; no smoke at all; or even any odor of smoke. In addition; I opened both panels underneath and next to the lavatory sink and the conclusion was the same. In addition; the small black fire extinguishing bottle underneath the lavatory sink had not been discharged. Meaning the tips were still black versus silver.I returned to the flight deck; reported my findings to the captain; and once again we determined no diversion was necessary or warranted. Finally; the captain and I both determined it was safe to continue and obviously directed the F/a to not use that specific oven for the remainder of the flight. The remainder the flight was uneventful.

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Original NASA ASRS Text

Title: During a Part 121 flight in cruise; a galley oven produced enough airborne smoke to activate a nearby lavatory smoke detector due to the lavatory door having been left open.

Narrative: After level off at FL340 and approximately 1+30 hours into the flight the Flight Attendant (F/A) in the aft galley called the flight deck and reported to the Captain that the smoke detector alarm in the aircraft left aft lavatory had been activated (was sounding off). Normally; pilot thought where there is smoke there is the possibility of fire. So; the Captain transferred control of the aircraft navigation and radios to me while she continued to question the F/A on the situation; prepared to run the appropriate QRH checklist; talk to all appropriate individuals and agencies; and get the aircraft on the ground safely and expeditiously. Mind you this is all happening simultaneously.During the subsequent questioning of the F/A the Captain asked; 'Did you or do you see fire now or ANY indications of fire?' The F/A response was no. In addition; the Captain asked; 'Is there still smoke; or has it dissipated?' F/A response was the smoke had completely dissipated and the smoke detector alarm is no longer sounding and had been reset.Subsequently; the Captain informed me of the conversation with the F/A and again that there was NO fire; indications of fire; the smoke had completely dissipated; the smoke detector alarm was no longer sounding; and had been reset. Therefore; the Captain made the decision; which I FULLY supported; that no diversion was necessary. However; we complied with the 'two person in the cockpit rule'; and I went to the aft galley/lavatories to check things out as an added precaution.I asked the F/A what happened? The F/A stated; that passenger hot meals were being cooked for the first service. For some unknown reason one of the aft galley oven doors was left open and started smoking. In addition; the aircraft left aft lavatory door was also open. The F/A believed the combination of the oven door left open; the oven smoke; and heat somehow triggered the lavatory smoke detector alarm to sound.I investigated the lavatory in question and found no fire; indications of fire; no smoke at all; or even ANY odor of smoke. In addition; I opened BOTH panels underneath and next to the lavatory sink and the conclusion was the same. In addition; the small black fire extinguishing bottle underneath the lavatory sink had NOT been discharged. Meaning the tips were still black versus silver.I returned to the flight deck; reported my findings to the Captain; and once again we determined no diversion was necessary or warranted. Finally; the Captain and I BOTH determined it was safe to continue and obviously directed the F/A to NOT use that specific oven for the remainder of the flight. The remainder the flight was uneventful.

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.