WASHINGTON (CNN) -- A Northwest Airlines flight from San Diego, California, overshot the Minneapolis, Minnesota, airport by about 150 miles Wednesday evening, and federal investigators are looking into whether the pilots had become distracted, as they claimed, or perhaps fell asleep.
A view of the city shortly after takeoff from Minneapolis-St. Paul International Airport.
Air traffic controllers lost radio communication with the Airbus A320, carrying 147 passengers and an unknown number of crew, when it was flying at 37,000 feet, according to the National Transportation Safety Board.
There was no communication with the airplane for more than an hour as it approached the airport, the board said. An FAA spokesman said the agency was tracking the airplane on radar, so it knew the aircraft's position during the period without radio contact.
The aircraft flew over its intended destination -- Minneapolis-St. Paul International/Wold-Chamberlain Airport -- and continued northeast for approximately 150 miles over the next 16 minutes. The airport's controllers then re-established communication with crew members, who said they had become distracted, the safety board said.
"The crew stated they were in a heated discussion over airline policy and they lost situational awareness," the board said in a news release.
A federal official, who asked not to be identified, told CNN that air traffic controllers in the Denver area had communicated with the pilot, but during a subsequent communication the pilots were "nonresponsive." The plane was handed off to controllers in Minneapolis as a NORDO, the designation for "no radio communications."
In an effort to contact the pilots, the Federal Aviation Administration contacted the airline and had the airline attempt to reach the pilots through its dispatcher, the source said.
A board spokesman said the agency is examining all possible explanations for the mishap, including whether the pilots may have fallen asleep.
The safety board said it is scheduling an interview with the crew and has secured the plane's cockpit voice recorder and flight data recorder for examination. Cockpit voice recorders record cockpit conversations and other noises.
Reported instances of two pilots falling asleep are rare but have happened. In August, the safety board concluded its investigation into a February 13, 2008, incident in which two pilots on board a Go airlines flight fell asleep and traveled 26 miles beyond the destination of Hilo, Hawaii, before waking up and contacting air traffic controllers.
Northwest Airlines is part of Delta Air Lines, which issued a statement Thursday saying it is "cooperating with the FAA and NTSB in their investigation as well as conducting our own internal investigation. The pilots have been relieved from active flying pending the completion of these investigations."
It said the plane, Northwest Flight 188, landed safely in Minneapolis just after 9 p.m.
Delta suffered another major embarrassment this week when a Delta pilot landed a passenger jet on a taxiway at Atlanta-Hartsfield International Airport instead of the runway. The NTSB also is investigating that mishap.