Air traffic controllers lost radio contact for more than an hour
A pilot on the US plane that overshot its destination by 150 miles has said the incident was "not serious" and passenger safety was not an issue.
Richard Cole told the Associated Press news agency outside his home in Oregon that it was not unusual for planes to lose contact with ground control.
Contact with the Northwest Airlines jet was lost for more than an hour before it landed in Minneapolis on Wednesday.
The White House has said it was kept informed of the flight's situation.
Richard Cole told AP: "It was not a serious event, from a safety issue.
"I would tell you more, but I've already told you way too much."
He stressed again that reports the pilots had fallen asleep were wrong.
"We were not asleep, we were not having an argument, we were not having a fight."
When asked why it had taken him and fellow pilot Timothy Cheney so long to respond to radio calls, Mr Cole said: "I can tell you that airplanes lose contact with the ground people all the time.
"It happens. Sometimes they get together right away; sometimes it takes a while before one or the other notices that they are not in contact."
Older data system
Jets from the National Guard were put on alert to chase the airliner amid fears it may have been hijacked, although they did not take off.
White House spokesman Nick Shapiro said it had been informed of the situation and had been monitoring it closely.
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However, Mr Shapiro would not say whether President Barack Obama had been told of the incident.
The investigation into the incident has begun, with assessment under way of the plane's data recorders.
However, the Airbus A320 in question reportedly has an older recording system said to contain only the last half hour of Flight 188.
Both pilots have been suspended pending the inquiry.
The plane was heading from San Diego to Minneapolis carrying 147 passengers.
Air traffic controllers lost radio contact with the plane approximately an hour before it was due to reach its destination of Minneapolis-St Paul International/Wold-Chamberlain Airport.
The plane missed its intended stop and continued on for a further 16 minutes before controllers managed to speak to the pilots.