An experienced US pilot who ranted about al Qaeda and bombs before being restrained by passengers is believed to have suffered a panic attack, with friends and colleagues describing him as a "gentleman" and a "consummate professional".
JetBlue pilot Clayton Frederick Osbon, 49, has been suspended from work and charged over his actions on the New York to Las Vegas flight earlier this week.
While his condition was originally reported only as a medical emergency, officials said Mr Osbon had suffered a panic attack, US ABC News reported.
Neighbours in Mr Osbon's New York City apartment block said they were sad to hear about his breakdown on flight 191, and described his actions as totally out of character.
Mr Osbon's land lady Wanda Serra said he had lived in her two-storey apartment building on 150th Avenue for about 11 years.
"I'm sick about it," she told Newsday.
"He's a gentleman. He wouldn't be here [in her building] if he wasn't."
She said Mr Osbon called her "bonbon", an affectionate term for grandmother.
Fred Capace, 37, has lived next door to Mr Osbon for many years and the pair sometimes watched football games together.
"I just hope he's OK," Capace said.
"He's just a stand-up regular guy."
Mr Capace said Mr Osbon was a fan of the Green Bay Packers football team, 1970s rock music and he loved his job.
Elton Stafford, who lives across the street from Osbon, also expressed his shock.
"Clayton's a great guy. Loves to have a good time, loves the outdoors. He just loves people," Mr Stafford said. "They're the kind of neighbours that everybody wants."
Mr Osbon's wife, Connye Osbon, warned there were several sides to every story.
"Just keep that in mind," she told ABC News, adding she didn't have any insight into what happened.
"I have no idea what's going on. I haven't spoken with him."
JetBlue CEO Dave Barger said there had never been signs of problems with Mr Osbon.
"The captain's now in the hands of medical care, obviously, under the custody of the FBI," Mr Barger told NBC's Today program.
"I've known the captain personally for a long period of time, and there's been no indication of this at all."
He described Mr Osbon as a "consummate professional."
JetBlue said the pilot had been taken off active duty while the incident was reviewed.
He was charged with interfering with flight crew instructions.
According to several reports Mr Osbon left the controls of the Airbus A320, which was carrying 135 passengers, paced around the plane and made threats of a plane crash before becoming angry at being locked out of the cockpit.
Passenger Jason Levin said the captain was "banging on the door like a bounty hunter, trying to knock down the door."
Mr Levin, who helped subdue the captain with several other men while the co-pilot made an emergency landing in Amarillo, Texas, said it appeared he had a "mental breakdown".
"Something in his brain wasn't right. It wasn't a terrorist act. I don't think he had bad intentions," Mr Levin told Newsday.
Another passenger, David Gonzales, said he rushed to help when he saw flight attendants struggling to hold Mr Osbon back as he rushed towards the emergency exit.
Mr Gonzales said the pilot told them: "You'd better start praying right now," and was shouting about al- Qaeda, a bomb, and saying the plane was going down.
"I was actually the one that took him down. I noticed he was very erratic," Mr Gonzalez told ABC News.
"He was pinned against the door. I was afraid he was going to knock down the door."
Many news reports have likened Mr Osbon's breakdown to that of JetBlue attendant Steven Slater, who got angry at passengers, told them off over the loudspeaker and made his own emergency exit in 2010.
smh.com.au with Reuters and AP
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