Investigators scramble to figure out wayward Northwest flight

WASHINGTON — Federal investigators are trying to determine what happened aboard a Northwest Airlines jetliner whose crew flew 150 miles past its destination while air traffic controllers, other pilots and even a flight attendant back in the cabin tried to get their attention.

Investigators don't know whether the pilots may have fallen asleep, but National Transportation Safety Board spokesman Keith Holloway said Friday that fatigue and cockpit distraction will be looked into.

The plane's flight recorders were brought to Washington on Friday, but the cockpit voice recorder is an older model that contains only the last 30 minutes of conversation. That makes the investigation more difficult since that time would be taken up by the flight back to Minneapolis — the intended destination — and the landing there Wednesday night.

Flight 188's recorders were delivered to the NTSB's Washington office. The pilots, both temporarily suspended, are to be interviewed by investigators next week. The airline, acquired last year by Delta Air Lines, is also investigating.

The crew told authorities they were distracted during a heated discussion over airline policy, the NTSB said.

Wednesday night, the airliner with more than 140 passengers aboard zoomed past Minneapolis at 37,000 feet at what was supposed to be the end of a flight from San Diego. Worried about who was actually at the controls, officials asked the crew to prove who they were by executing turns after they finally were contacted.

On the ground, police and FBI agents prepared for the worst, and the Air National Guard put fighter jets on alert at two locations as the drama unfolded.

Pilots from two other planes in the vicinity were finally able to reach the pilots using a different radio frequency, a controllers union spokesman said. A flight attendant in the cabin also was able to contact them by intercom, said a source close to the investigation who wasn't authorized to talk publicly and spoke on condition of anonymity.

By that time, the Airbus A320 was over Eau Claire, Wis., and the pilots had been out of communication with air traffic controllers for over an hour. They turned back and landed safely in Minneapolis, the plane's scheduled destination.

The plane passed over Minneapolis at 37,000 feet just before 8 p.m. local time. Contact with controllers wasn't established until 14 minutes later, NTSB said.

Air traffic controllers in Denver had been in contact with the pilots as they flew over the Rockies, FAA spokeswoman Laura Brown said. But as the plane got closer to Minneapolis, she said, "the Denver center tried to contact the flight but couldn't get anyone."

Denver controllers notified their counterparts in Minneapolis, who also tried to reach the crew without success, Brown said.

Officials suspect Flight 188's radio might still have been tuned to a frequency used by Denver controllers even though the plane had flown beyond their reach, said Doug Church, a spokesman for the National Air Traffic Controllers Union. Controllers worked throughout the incident with the pilots of other planes, asking them to try to raise Flight 188 using the Denver frequency, he said

That was unsuccessful until two pilots working with Minneapolis controllers finally got through just before the plane turned around, Church said. Minneapolis controllers don't have the capability of using the Denver frequency, but pilots do, he said.

After re-establishing contact with the plane, controllers asked the pilot in charge to execute a series of turns to show he was in control of the aircraft, Church said.

"Controllers have a heightened sense of vigilance when we're not able to talk to an aircraft. That's the reality post-9/11," he said.

Passenger Lonnie Heidtke said he didn't notice anything unusual before the landing except that the plane was late.

The flight attendants "did say there was a delay and we'd have to orbit or something to that effect before we got back. They really didn't say we overflew Minneapolis. ... They implied it was just a business-as-usual delay," said Heidtke, a consultant with a supercomputer consulting company based in Bloomington, Minn.

Once on the ground, the plane was met by police and FBI agents. Passengers retrieving their luggage from overhead bins were asked by flight attendants sit down, Heidtke said. An airport police officer and a couple other people came on board and stood at the cockpit door, talking to the pilots, he said.

"I did jokingly call my wife and say, 'This is the first time I've seen the police meet the plane. Maybe they're going to arrest the pilots for being so late.' Maybe I was right," Heidtke said.

The pilots' explanation that they were distracted by shop talk "just doesn't make any sense," said Bill Voss, president of the Flight Safety Foundation in Alexandria, Va. "The pilots are saying they were involved in a heated conversation. Well, that was a very long conversation."

The FAA is updating rules governing how many hours commercial pilots may fly and remain on duty. The NTSB also cautioned government agencies this week about the risks of sleep apnea contributing to transportation accidents.

In January 2008, two pilots for go! airlines fell asleep for at least 18 minutes during a midmorning flight from Honolulu to Hilo, Hawaii. The plane passed its destination and was heading out over open ocean before controllers raised the pilots. The captain was later diagnosed with sleep apnea.