The flight,an airbus A320, carrying 144 passengers was flying from San Diego to Minneapolis at 37,000 feet when it lost radio contact between 8pm and 9.15 pm.
On landing safely on Wednesday, Oct 21, the two pilots who underwent breathalyzer test, informed that a heated discussion on airline policy distracted them and they lost situational awareness, said the National transportation Safety Board(NTSB).
The NTSB said that it would review the plane's flight data and voice recorders and interview the pilots.Investigation would also include the possibility of crew fatigue to see if the pilots were tired.
Fearing a case of hijacking, airport police boarded the plane in Minneapolis while military authorities were alerted and fighter jets put on standby status temporarily, the North American Defense Command said.
Earlier on Monday, Oct 19, a Delta Boeing 767 landed on taxiway instead of its assigned runway at Atlanta's Hartsfield airport.