B777 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 190; Flight Crew Total 11282; Flight Crew Type 11282
Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
We were cleared to taxi to Runway 19C and hold short. The First officer (FO) read back both the taxi and the hold short instructions. While at the hold short; the tower asked us to confirm that we were indeed holding short. We confirmed that we were. While waiting for some corporate jets to land; we discussed the fact that it seemed the Tower couldn't see us. He had asked one airplane where he was; and where he was exiting the runway; plus he asked us about holding short. We discussed the fog and that perhaps the tower's visibility was restricted or nil. The ground vis was ok; current weather was reported as: KIAD 21007KT 1SM R01R/P6000FT BR OVC004 05/04 A3007 RMK AO2 SLP183 T00500044.We were instructed to line up and wait; [then] we were cleared for takeoff. The Tower transmitted; '[Company]; let me know when you're rolling.'  Our speed at that time was 120 KIAS; according to the Captain Pilot Flying (PF). (I'm not 100% sure; but I think V1 was around 138K. Our TOGW was about 635K). On climb-out; the Captain and I agreed that as soon as we heard '[Company]' we were expecting a tower-directed abort.  I thought that perhaps because of the heavy fog and apparent lack of visibility; there was a Tenerife-type runway incursion in the making.  All this happened at 120 knots.It was not the best time for the Tower to ask us a relatively routine question. I'm sure the controller has a passing familiarity with how takeoff aborts are conducted in the cockpit; but he probably has no idea of the huge emphasis placed on pilots (at least [Company] pilots) with the go-no go decision; and how incredibly focused and critical everything becomes in the high-speed regime.
B777 First Officer reported the flight crew was distracted at a critical time in the takeoff roll when Tower radioed with a non-essential question.