WASHINGTON: A Northwest Airlines flight carrying 144 passengers from San Diego to Minneapolis lost contact with air controllers for more than an hour and overflew its destination by 150 miles, officials said on Thursday.

The National Transportation Safety Board said the two pilots of Flight 188, an Airbus A320, told authorities after landing safely on Wednesday night that they had become distracted during a "heated discussion about airline policy."

The NTSB said on Thursday it would review the plane's flight data and voice recorders and interview the pilots. Among other issues, investigators will explore crew fatigue to see if the pilots were tired, the NTSB said.

Northwest is owned by Delta Air Lines, which said the pilots had been relieved from active flying pending completion of the NTSB investigation and an internal probe by Delta.

Safety board investigations can take several months to complete.

The plane was flying at 37,000 feet when it lost radio contact between 8 p.m. and 9:15 p.m. EDT.

Flight 188 was 150 miles off course by the time the crew re-established communications and requested permission to turn around, officials said.

Airport police boarded the plane in Minneapolis to ensure there had not been a hijacking or other criminal activity, a spokesman for the Minneapolis-St Paul Airport said.

Military authorities were alerted during the incident and put fighter jets on stand-by status temporarily, the North American Aerospace Defense Command said.

It was the second unusual incident involving a U.S. airliner this week.

On Monday, a Delta Boeing 767 with 182 passengers landed on a taxiway instead of its assigned runway at Atlanta's Hartsfield airport. The taxiway, which was parallel to the runway, was active but cleared of ground traffic.

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