Date: 201912
Local time of day: 0601-1200
Location: ATL.Airport, GA
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ATL
Second aircraft: Commercial Fixed Wing
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Captain; Pilot Flying
Anomaly: Conflict Ground Conflict; Critical; Ground Incursion Runway
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Rejected Takeoff
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: We were instructed to line up and wait with traffic to cross down field on Runway 27R. Tower instructed a host of aircraft to cross the runway. After all of the aircraft had crossed; Tower then cleared us for takeoff. I was PM; the Captain was PF. Around 80 knots I saw a Air Carrier Y edging out onto the runway and [I] verbalized this to the Captain. Tower then said something like 'Air Carrier Y; what are you doing? Stop right there.' This; coupled with the fact that the Air Carrier Y continued moving out onto the runway was enough reason for the Captain to call a rejected takeoff (now at around 100 knots). Tower did not instruct us to abort. We safely came to a stop and exited the runway and completed the QRH and appropriate checklists. It seemed as though Tower assumed Air Carrier Y had crossed when we had been cleared for takeoff; but they had actually not even begun to cross the runway. Additionally; it's tough to see Taxiway Papa (where Air Carrier Y) while you're at the approach end of 27R. Regardless; we shouldn't have been cleared to take off or Air Carrier Y's clearance to cross the runway should have been cancelled. I do not know what happened in the Tower; but we stopped as soon as we saw it was unsafe to continue.


Second narrative: We were cleared to lineup and wait on 27R in Atlanta while several aircraft were cleared to cross down field. When the runway was clear; we were given a takeoff clearance by tower. (We saw no aircraft on the runway when we received the takeoff clearance.) As we passed through 80 knots; my FO/PM brought to my attention that Air Carrier Y was crossing the runway. It took me a moment to process that we had a runway incursion. I initiated a rejected takeoff at about 100 knots. My FO informed tower of our abort; and we exited the runway on the highspeed Taxiway M12. I made a PA to inform the passengers that we discontinued the takeoff due to something on the runway; to stay seated with their seatbelts fastened; and that we would go back for takeoff shortly. We completed the RTO and after landing checklists and contacted dispatch. I checked with the FA; and all crew members were good to continue. We continued the flight with no further interruptions.We thought that Air Carrier Y mistakenly crossed 27R at P without a clearance after we were given the takeoff clearance. However; it appears that ATL Tower had cleared Air Carrier Y to cross 27R along with several other aircraft while we were holding in position. About 60 seconds after Air Carrier Y was given the clearance to cross; we were given the Takeoff clearance. Neither Tower; nor we realized that there was an aircraft that had not crossed the runway yet.If Air Carrier Y was not ready to cross the runway; they should have informed Tower or not have accepted the runway crossing Clearance. They crossed the runway about 90 seconds after receiving the Clearance; and we were on the takeoff roll with all exterior lights on. Tower needed increased vigilance; and we as a flight crew could have been proactive by noticing that an aircraft had not crossed the runway yet.


Synopsis: Air carrier flight reported a rejected takeoff at about 100 knots at ATL airport due to a ground conflict with another air carrier crossing their runway.