Date: 201309
Local time of day: 0601-1200
Location: SEA.Tower, WA
Flight conditions: VMC
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
ATC / advisory: Tower SEA
Reporter organization: Air Carrier
Reporter function: Relief Pilot; First Officer
Human factors: Confusion; Situational Awareness; Distraction
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: We were number three in line for takeoff on Runway 16L. SEA Tower crossed two 737 aircraft in front of us across 16L for departure. Two other aircraft had landed on 16R and were holding short of the 16C near the departure end. The two aircraft ahead of us departed from 16C and Tower cleared us to lineup and wait on 16L; commenting that; 'Aircraft would be crossing downfield prior to your departure.' It is unclear if they were addressing us or another aircraft in the takeoff queue. We were expecting to wait for the aircraft to cross downfield before our departure. A B737 landed on 16R and was cleared along with a downfield B737 and an Airbus aircraft to cross 16C to hold short of 16L. We were then cleared for takeoff on 16L. It was clear to us that there were aircraft moving towards our runway at the departure end as we began our takeoff roll. As we started the roll Tower cleared an aircraft to cross 16L. The Pilot Flying exclaimed that; 'They just cleared that guy to cross our runway'; referring to the aircraft downfield. We advised Tower that we were taking off from 16L. Tower re-advised that we were clear for takeoff. Tower then repeated another clearance to cross 16L to a B737 and another aircraft? (Reviewing the recordings of Tower transmissions would be extremely useful). An aircraft then acknowledged the clearance to cross 16L. Discussion in the cockpit quickly turned to whether the aircraft up field were holding short; cleared to cross; or crossing our runway. The Pilot Monitoring missed the 100 knot call as we were all focused completely outside the cockpit attempting to judge the threat. Do you sense the confusion here? Keep in mind that we heard at least one clearance for another aircraft matching the call sign of aircraft holding short of our runway to cross our runway as we neared 100 KIAS. We continued to monitor the aircraft moving towards our runway during the entire takeoff roll. We lifted off and Tower cleared us to switch to Departure. We advised Tower that we didn't like the call they made in the middle of our takeoff roll; they then replied that the aircraft they cleared to cross our runway was crossing behind us. We then heard another call on Tower frequency saying that; 'We don't like it when our gear is down;' referring to the fact that our entire crew was so distracted by the incident that we failed to raise the gear after takeoff until almost 1;000 feet (this call was probably made from another aircraft; the inappropriate comment is not the issue).


Second narrative: Tower cleared us to line up and wait 16L for crossing traffic. After an extended time on the runway with no traffic crossing; Tower cleared us for takeoff. During the takeoff roll I heard tower clear first one; then another aircraft to cross 16L. I announced to the Captain that Tower cleared him to cross our runway. The Captain told the Tower we were on our takeoff roll and Tower responded the traffic would cross behind us. None of us heard any 'cross behind' or 'cross after' instructions from ATC. At least one of the aircraft announced they were holding short for us. The two aircraft appeared to be on taxiways P and Q which means the one on P cannot see down the runway due to the severe angle. As the Pilot Flying; I was a moment away from initiating a high speed abort at 130 knots (V1 160; Vr 166). After departing; all three pilots forgot to call positive rate; gear up; but the airplane that said he was holding short for us (we recognized the same voice) radioed that our gear was still down. This event had unthinkable potential for disaster! Besides the Tenerife potential; if we aborted the takeoff; we would have still been faced with brake temperatures in the melt zone (GW 567.4  130 knots just before I almost aborted) with a probable full evacuation of 284 souls with several aircraft in close proximity.


Synopsis: B777 flight crew departing Runway 16L at SEA reports hearing the Tower clear other aircraft to cross 16L and continue the takeoff but fear an incursion. The crew is so distracted that the landing gear is forgotten until another crew informs them over the radio.