The JetBlue plane is shown. Reuters

The JetBlue pilot who had a mental breakdown midair on Flight 191 has been suspended from duty while the FBI investigates the situation.

Dave Barger, the CEO of JetBlue, said the incident was being investigated as to why the pilot acted erratically, forcing the plane heading to Las Vegas to have an emergency landing in Amarillo, Texas.

Clayton Osbon, the captain, began acting strangely and was ejected from the cockpit by the co-pilot. He was subdued by passengers after repeatedly banging on the locked cockpit door, trying to get back in.

He has been removed from all active duty and responsibilities pending further investigation, JetBlue spokeswoman Tamara Young said to Reuters.

Flight 191 was diverted to Texas Tuesday due to a 'medical situation' on board involving the captain.

The 49 year old, 12 year veteran ran through the cabin screaming we're all going down and say your prayers.

Four men subdued the pilot using seat belt extenders and zip tie handcuffs until the co-pilot could safely land the plane. Passenger Tony Antolino said the pilot became almost delusional.

People behind me, a bunch of big guys, started going up there and trying to help, and we found out that the guy banging was actually the pilot, and he was trying to get into the cockpit because the other co-pilot had locked him out, passenger Grant Heppes told Reuters.

Barger said there were no previous signs of mental issues with the JetBlue pilot and that he was always a consummate professional.

The captain's now in the hands of medical care, obviously, under the custody of the FBI, Barger told the 'Today' program. I've known the captain personally for a long period of time, and there's been no indication of this at all.

Friends of the JetBlue pilot have rushed to his defense.

Clayton's a great guy. Loves to have a good time, loves the outdoors. He just loves people, Elton Stafford, a neighbor of the captain, said to CBC. They're the kind of neighbors that everybody wants.

The JetBlue pilot remains in a medical facility in Amarillo, Texas.