B777 Undifferentiated or Other Model
Flight Crew Last 90 Days 154; Flight Crew Total 17200; Flight Crew Type 1318
Situational Awareness; Distraction
Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors
We had a somewhat complicated taxi route to runway 10L. This distracted the crew as we taxied out for departure.  It was a routine takeoff.  After takeoff the Captain called for flaps up and then the After Takeoff checklist.  I couldn't see the checklist from the second observer seat but the other relief pilot told me that the Before Takeoff checklist came up. It ends up that we departed without completing the Before Takeoff checklist.  I was focused on the taxi route and I could only see the Captain's Primary Flight Display (PFD) from my seat but I still should have noticed that we had not completed the checklist before departing.During transition training our [instructor] taught us to leave the checklist displayed on the First Officer's inboard screen until the Before Takeoff checklist is complete.  I think this is a great technique.  The other relief pilot in the primary observer's seat told me that the flying first officer had put his display back to NAV after completing the After Start checklist.  If he had followed the technique of leaving the checklist displayed until completing the Before Takeoff checklist it would have been easy to see that the checklist still needed to be accomplished.
A B777 First Officer reported; due to distractions; that their flight took off without completing the Before Takeoff checklist.