The agency also found problems with air traffic control practices, and it recommended that controllers use clearer language to alert flight crews of an emergency communication.
Federal officials said that the two Northwest Airlines pilots who overflew Minneapolis-St. Paul by more than 150 miles became so distracted by a conversation over flight schedules that they failed to hear repeated radio calls.
However, a report released Thursday by the National Transportation Safety Board also placed some blame for the errant flight on air traffic controllers, and it recommended changes in the way flight crews communicate with controllers.
The pilots failed to maintain radio communication because they became distracted by a conversation over changes to the process for requesting flight schedules -- changes resulting from the merger between Northwest and Delta Air Lines. The conversation was so engrossing that the pilots missed "at least nine messages regarding their position" as they neared the Minneapolis-St. Paul airport, and entered the airport without landing data entered into the flight management computer, the NTSB's findings said.
The two pilots, Timothy Cheney of Gig Harbor, Wash. and Richard Cole of Salem, Ore., had their licenses revoked in October, but can reapply for them in August. The pilots could not be reached to comment.
The NTSB's report ends a six-month investigation into the flight's errant path last October and confirms earlier reports, based on interviews with the flight crew, that pilots were not adequately focused on operating the Airbus A320. The flight from San Diego landed safely in Minneapolis with no injury to its crew and 144 passengers.
However, the report also found significant lapses by air traffic controllers, and recommended new communication procedures between flight crews and controllers.
The NTSB said in its statement Thursday that recent accidents and incidents "have demonstrated the clear hazards to aviation safety when pilots and air traffic controllers depart from standard operating procedures." In August, a midair collision of an airplane and a helicopter killed nine people over the Hudson River, and the crash last February of Pinnacle Airline Corp.'s Colgan Air flight 3407 near Buffalo, N.Y., left 50 people dead.
The crew of the Northwest Airlines flight did not communicate with air traffic controllers for 77 minutes, the NTSB found. According to the report, the Northwest pilots were not aware of some 25 attempts by controllers and the airline to contact them until a flight attendant used the intercom to inquire about the progress of the flight.
When a Minneapolis air traffic controller finally did reach the wayward flight, a pilot said, "Roger, we got distracted and we've overflown Minneapolis," according to the NTSB report. "We're overhead Eau Claire and would like to make a one-eighty and do arrival from Eau Claire."
The NTSB recommended that the Federal Aviation Administration require air traffic controllers to use more explicit phrases, such as "on guard," to make it clear that pilots are receiving emergency communications. A review of the air traffic recordings of the flight reveal that a Minneapolis controller did not announce that he was trying to reach the crew through an emergency frequency, the report said.
However, the loss of radio contact between flight crews and controllers is not unusual, and may be partly to blame for why air traffic controllers were slow to re-establish communication with the Northwest flight. In fact, the NTSB pointed out in its report that air traffic controllers can lose contact with pilots several times during an eight-hour shift. The frequency of such lost contacts "likely contributed to the controllers becoming complacent," the report said.
Anthony Black, a spokesman for Delta, said the airline is retrofitting all of its Airbus A320 aircraft to ensure that pilots receive both audio and visual signals from Delta's own radio dispatchers, thus making it less likely that messages will be missed.
Black said Delta is still conducting its own investigation in the flight.
The NTSB said in its statement Thursday that it plans to hold a three-day forum in May on "professionalism in aviation."
Chris Serres • 612-673-4308