Two pilots told federal investigators they were going over scheduling using their laptop computers in violation of company policy while their plane overflew their Minneapolis destination by 150 miles.
National Transportation Safety Board said in a statement Monday that the Northwest Airlines pilots said in interviews that they were not fatigued and didn't fall asleep after taking off from San Diego, as many aviation safety experts have said was likely.
The board said the pilots told investigators the first officer was instructing the captain on monthly flight crew scheduling. The pilots were out of communication with air traffic controllers and their airline for over an hour and didn't realize their mistake until contacted by a flight attendant.
Federal officials are investigating whether pilot fatigue was a factor in the incident. The plane landed safely Wednesday evening after crew members discovered their mistake and flew another 150 miles back.
None of the 147 passengers and crew were injured.
Northwest flight 188 was flying from San Diego to Minneapolis and lost radio contact with controllers before 7 p.m. on Wednesday, according to the National Transportation Safety Board officials. The jet flew about 150 miles past the Minneapolis airport before communications were re-established at 8:14 p.m., authorities said.
The Federal Aviation Administration said the crew told authorities they became distracted during a discussion. An NTSB spokesman, Keith Holloway, said, however, that the agency will look into whether fatigue played a role.
"We will look into fatigue issues," Holloway said. "We don't know" if the crew fell asleep, he said, calling that "speculative."
A spokesman for Delta, Northwest's parent company, said both pilots on-board have been suspended.