Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Time Pressure; Situational Awareness; Communication Breakdown; Confusion
ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action
Human Factors; Procedure
We were holding short of [Taxiway] 1 on Taxiway 2 at ZZZ. ATC cleared Aircraft Y into position and hold Runway XXL. In the meantime Aircraft Z was on short final to the same runway at approximately 1;500 ft. AGL (just a wag). Aircraft Y turned left on Taxiway 1 and crossed the hold lines for [Runway] XXL and continued till he came to a screeching stop as I assume he then saw the Aircraft Z coming down the ILS. Aircraft Y was well across the hold lines but had not crossed onto displaced threshold portion of the runway. ATC nor anybody else said anything. There was this weird silence; and without hearing anyone else saying anything I keyed the microphone and said 'Hey Aircraft Z go around;' and Aircraft Z immediately started a Go Around. Then finally ATC came on the radio and gave Aircraft Z; go around instructions; and told Aircraft Y that it'll be a few minutes for take off due to wake turbulence. Eventually Aircraft Y was cleared for take off and then we were cleared onto the runway. As we crossed the [Runway] XXL hold lines we saw fresh tire skid marks; approximately 20 ft. in length from Aircraft Y. Interesting thing is Aircraft Y never queried ATC during this event. We happened to have a jump seater commuting home and he provided me some data from the website Flight Aware. Flight Aware shows Aircraft Z at 475 ft. when they started to climb/Go Around; and ATC had previously cleared Aircraft Y to depart. On departure ATC said 'Sorry to Aircraft Z' and Aircraft Y acknowledged with 'Yeah we were confused.' I told/instructed Aircraft Z to 'go around;' after nobody else would say anything and the fact the two planes were on what appeared to be a collision course. It seemed as though ATC was unaware they had two planes going to the same runway.
Captain reported observing a ground conflict and advised a heavy aircraft on final to go around due to an aircraft that taxied across the runway hold lines.