The NTSB also said that flight attendants might be interviewed on Monday, and that it would not release further information for now.
The cockpit of an Airbus 320 airliner is shown above.
First officer Richard Cole has said he and the captain were not sleeping or arguing in the cockpit, but hasn't explained their lapse in response and the detour.
"We were not asleep; we were not having an argument; we were not having a fight," Cole said.
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