Passengers aboard and early morning flight bound from New York to Las Vegas first noticed something wrong when the plane's top pilot came out of the cockpit unannounced.
They say he didn't close the door and tried to force his way into an occupied bathroom.
The JetBlue captain's co-workers tried to calm him as he became more agitated. They coaxed him to the back of the plane while making sure - above all - that he didn't get back near the plane's controls.
The tense situation climaxed when the pilot sprinted up the cabin's aisle screaming, "They're going to take us down!" and urging confused passengers to pray.
Airline officials say the captain had a "medical situation." He was restrained until the plane landed safely in Amarillo, Texas.