US NTSB investigators say the two pilots on a Northwest Airlines A320 (N02374) that was out of radio communications with air traffic controllers for more than an hour the night of 21 October were immersed in a discussion of new scheduling procedures as the aircraft overflew its destination airport by more than a hundred miles at cruise altitude.
According to NTSB interviews held on 25 October with the captain, age 53, and first officer, age 54, fatigue and sleep were not issues during the flight from San Diego to Minneapolis-St. Paul that day, nor had there been a "heated argument". According to an earlier NTSB report, the pilots had told the FBI and airport police after landing that evening that they had been in a "heated discussion over airline policy and they lost situational awareness."
Rather, the pilots said they had been involved in a "concentrated period of discussion where they did not monitor the airplane or calls from (air traffic control) even though both stated they heard conversation on the radio. Also, neither pilot noticed messages that were sent by company dispatchers," says the NTSB.
In particular, the discussions focused on a new monthly crew flight scheduling system put in place after the merger of Northwest and Delta Airlines, with each pilot using a personal laptop computer as part of the discussion.
"The first officer, who was more familiar with the procedure was providing instruction to the captain," says the NTSB, adding that the "use of personal computers on the flight deck is prohibited by company policy."
The pilots said neither was aware of the aircraft's position until a flight attendant called about five minutes before they were scheduled to land and asked about the estimated time of arrival (ETA). "The captain said, at that point, he looked at his primary flight display for an ETA and realized that they had passed MSP," the NTSB reports. "They made contact with ATC and were given vectors back to MSP."
Though flight data recorder information is available for the entire flight, the cockpit voice recorder covered only the final 30min of the flight, starting from the final approach. "Investigators are examining the recorded parameters to see if any information regarding crew activity during the portion of flight where radio contact was lost can be obtained," says the NTSB.