An airline captain who was restrained after an apparent mental breakdown mid-flight gave no previous cause for concern, his boss has said.
Captain Clayton Osbon has been suspended after ranting about al-Qaeda and being locked out of the cockpit on Tuesday's New York to Las Vegas flight.
JetBlue chief executive Dave Barger said he had known Mr Osbon, who is now in a medical facility, for a long time.
Flight 191 was diverted to make an emergency landing in Amarillo, Texas.
Nothing in Mr Osbon's records suggested he could be a risk, JetBlue chief executive Dave Barger told NBC News.
"I've known the captain personally for a long period of time and there's been no indication of this at all," Mr Barger said.
He added that the pilot was a "consummate professional".
Mr Barger said the crew and passengers "just did a great job" in what was a "tough situation at altitude".
Mr Osbon came out of the cockpit, left the door open and tried to force his way into an occupied bathroom during Tuesday's episode, passengers say.
As he became more agitated, crew members tried to calm him down and move him away from the cockpit.
He began running through the aisles, calling on passengers to pray and shouting: "They're going to take us down!"
One passenger, Don Davis, said: "Nobody knew what to do because he is the captain of the plane. You're not just going to jump up and attack the captain."
Eventually, several male passengers tackled Mr Osbon to the ground and restrained him using seat belt extensions and zip-tie handcuffs.
An off-duty pilot who happened to be on board took over and helped land the plane.
Tony Antolino, one of the passengers who helped restrain the captain, said: "Clearly, he had an emotional or mental type of breakdown.
"He became almost delusional. A group of us just jumped up instinctually and grabbed him and put him to the ground."
Another passenger, Gabriel Schonzeit, told the Amarillo Globe-News: "He started screaming about al-Qaeda and possibly a bomb on the plane and Iraq and Iran and about how we were all going down."
Once on the ground in Amarillo, passenger Grant Heppes said each passenger was interviewed after leaving the plane.
An FBI spokeswoman said the agency was investigating the incident, along with federal air and transport safety regulators, airport police and local police.
The Federal Aviation Administration has said it is likely to review whether Mr Osbon should be certified healthy enough to work.
Pilots must have a first-class medical certificate in order to fly. It is renewed every six months to one year, depending on the pilot's age.
The medical test includes a physical examination and questions about the pilot's psychological condition.
A few weeks earlier, an American Airlines attendant was taken off a plane after she began rambling about 9/11 and that she was afraid the flight would crash.
Aviation expert John Cox told the Associated Press news agency that he could only think of three or four cases in the last 40 years when a crew member had become mentally incapacitated during a flight.