Narrative:

There were a total of four pilots on this flight; captain; first officer; and two iros (international relief officers). After several hours in cruise flight; the captain noticed that the #1 engine oil quantity was lower than #2 and appeared to be decreasing at a rate of 1 quart per hour. During the crew change briefing approximately 6 hours into the flight the captain advised myself and the other international relief officer of the issue. As the flight continued; the rate of oil consumption remained steady and we; the iros; contacted dispatch; maintenance; and flight operations and briefed them on the issue. We also briefed the flight attendants regarding the ongoing issue and the potential for a precautionary diversion if the oil quantity continued to decrease. Additionally; we kept the captain informed of the situation during his rest break.the captain returned to the flight deck about 1 hour prior to being abeam [a suitable alternate]. We briefed the captain that the oil quantity in the #1 engine had reached zero and that the oil pressure had been continually fluctuating between 54-59 psi versus the #2 engine oil pressure being steady at 75 psi. We again contacted dispatch and flight operations and discussed our options. The captain advised them that we believed that the safest course of action would be to divert before it became necessary to shut the engine down and then have to potentially divert into a less desirable 'closest suitable airport in point of time.'we advised the flight attendants and passengers of the situation and our decision to divert in the interest of safety. Since we did not know the full extent of the issue that resulted in the loss of all indicated oil quantity in the #1 engine; we advised ATC that we were [diverting] and requested clearance to [the suitable alternate]. We completed an uneventful approach and landing and taxied to the ramp. The #1 engine remained functional at all times during the flight and we did not reduce or limit its operation at any time.maintenance personnel inspected the engine and observed a significant amount of oil residue dripping out of the engine cowl; and once the cowling was opened they observed a large area of the external engine components covered in oil. During the next hour we worked with operations; maintenance; and customer service to ensure that the customers were kept up to date on the progress of the situation. After approximately one hour on the ramp [headquarters] made a decision to cancel the flight and the passengers were transported via bus from the remote ramp area to the terminal.

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Original NASA ASRS Text

Title: Boeing 787-900 First Officer reported a steady deterioration of the #2 engine oil quantity accompanied by fluctuating oil pressure. A decision was made to divert before the situation required the engine to be shut down.

Narrative: There were a total of four pilots on this flight; Captain; First Officer; and two IROs (International Relief Officers). After several hours in cruise flight; the Captain noticed that the #1 engine oil quantity was lower than #2 and appeared to be decreasing at a rate of 1 quart per hour. During the crew change briefing approximately 6 hours into the flight the Captain advised myself and the other IRO of the issue. As the flight continued; the rate of oil consumption remained steady and we; the IROs; contacted Dispatch; Maintenance; and Flight Operations and briefed them on the issue. We also briefed the Flight Attendants regarding the ongoing issue and the potential for a precautionary diversion if the oil quantity continued to decrease. Additionally; we kept the Captain informed of the situation during his rest break.The Captain returned to the flight deck about 1 hour prior to being abeam [a suitable alternate]. We briefed the Captain that the oil quantity in the #1 engine had reached zero and that the oil pressure had been continually fluctuating between 54-59 PSI versus the #2 engine oil pressure being steady at 75 PSI. We again contacted Dispatch and Flight Operations and discussed our options. The Captain advised them that we believed that the safest course of action would be to divert before it became necessary to shut the engine down and then have to potentially divert into a less desirable 'closest suitable airport in point of time.'We advised the Flight Attendants and passengers of the situation and our decision to divert in the interest of safety. Since we did not know the full extent of the issue that resulted in the loss of all indicated oil quantity in the #1 engine; we advised ATC that we were [diverting] and requested clearance to [the suitable alternate]. We completed an uneventful approach and landing and taxied to the ramp. The #1 engine remained functional at all times during the flight and we did not reduce or limit its operation at any time.Maintenance personnel inspected the engine and observed a significant amount of oil residue dripping out of the engine cowl; and once the cowling was opened they observed a large area of the external engine components covered in oil. During the next hour we worked with Operations; Maintenance; and Customer Service to ensure that the customers were kept up to date on the progress of the situation. After approximately one hour on the ramp [Headquarters] made a decision to cancel the flight and the passengers were transported via bus from the remote ramp area to the terminal.

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.