Incident Overview
On April 7, 2016, at 1836 central daylight time, a runway incursion occurred on runway 35L at Dallas-Fort Worth International Airport (DFW), Dallas, Texas. A Boeing 737-800, registration N896NN, operated by American Airlines as flight 2408 (AAL2408), was on its takeoff roll while an Embraer 505, registration N304QS, operated by NetJets Aviation as flight EJA304, crossed the runway downfield. The closest proximity between the two aircraft was approximately 2,800 feet when the Boeing's speed was about 120 knots. Visual meteorological conditions prevailed, and there were no injuries to passengers or crew on either flight.
Sequence of Events
EJA304 had landed on runway 35C and was instructed by the LE1 controller to taxi to the terminal via taxiways M and K8. At 1834:20, the pilot of EJA304 was directed to hold short of runway 35L on taxiway K8. An MD-82 operating as AAL2256 was holding short of runway 35L at taxiway EK, and an E170 operating as ENY3192 was taxiing to the gate after landing, instructed to taxi via taxiway M to taxiway EJ and hold short of runway 35L. At 1835:14, the LE1 controller cleared flight AAL2304 for takeoff on runway 35L. Eight seconds later, at 1835:22, the controller instructed the pilot of AAL2408 to line up and wait (LUAW) on runway 35L.
At 1835:39, the pilot of SKW5432, an arriving CRJ7 regional jet, reported outside the JOBBS airspace fix for landing on runway 35C. The LE1 controller responded with a takeoff clearance for SKW5432. However, the pilot of AAL2408, who was in position at the approach end of runway 35L, responded with "American twenty-four oh eight cleared for takeoff three five left." The LE1 controller did not respond to this incorrect readback.
As the previous departure (AAL2304) passed the taxiways intersecting runway 35L where aircraft were holding, the LE1 controller, in successive progression, directed the pilots of EJA304, AAL2256, and ENY3192 to cross runway 35L. All three pilots acknowledged the crossing clearance.
Runway Status Lights and Crossing
As AAL2408 began its takeoff roll, the Runway Status Lights (RWSLs) on runway 35L activated, illuminating the Runway Entrance Lights (RELs) at the hold short locations of the three aircraft that had been instructed to cross, as well as the Takeoff Hold Lights (THLs) at the approach end of the runway. The RELs provided a visual signal to the pilots holding short. The THLs provided a visual signal to the pilot of AAL2408 that the runway was occupied; however, data indicate that AAL2408 had progressed too far down the runway to observe the THLs by the time they illuminated. Of the three aircraft holding short, only EJA304 proceeded across runway 35L as AAL2408 departed.
Post-Incident Observations
After takeoff but before switching to departure control, the pilot of AAL2408 commented to the LE1 controller about the business jet that was on the runway during departure. As EJA304 cleared runway 35L, the Airport Surface Detection Equipment, Model X (ASDE-X) indicated AAL2408's speed to be 120 knots and the closest proximity between the two aircraft was approximately 2,800 feet. The ASDE-X did not alarm.
Controller Actions
During a System Service Review after the event, controllers identified a recent procedural change that required additional verbiage when issuing crossing instructions and an increased speech rate associated with increased workload.