The captain of a JetBlue plane screamed "They're going to take us down!" and rambled about al-Qaida as passengers pinned him to the floor while another pilot took charge to make an emergency landing. An off-duty airline captain who was a passenger on the flight entered the cockpit, locked the door and landed in Amarillo, Texas, the airline said in a statement. JetBlue Airways said the original pilot on flight 191 from New York's John F Kennedy international airport had been taken to hospital after suffering a "medical situation" on board. The captain had earlier stormed through his plane rambling about a bomb and threats from Iraq until passengers on the Las Vegas-bound flight tackled him just outside the cockpit, passengers said. He had seemed disoriented, jittery and constantly sipped water when he first marched through the cabin, then began to rant about threats linked to Iran, Iraq and Afghanistan after crew members tried to calm him down. "They're going to take us down! They're taking us down! Say the Lord's prayer!" the captain screamed, according to passenger Tony Antolino. Josh Redick, who was sitting near the middle of the plane, said the captain seemed "irate" and was "spouting off about Afghanistan and souls and al-Qaida". Gabriel Schonzeit, who was sitting in the third row, told the Amarillo Globe-News: "He started screaming about al-Qaida and possibly a bomb on the plane and Iraq and Iran and about how we were all going down." "A group of us just jumped up instinctually and grabbed him and put him to the ground," Antolino said after arriving in Las Vegas later Tuesday. "Clearly he had an emotional or mental type of breakdown." Antolino, a security executive, said he and three others pinned down the captain as he ran for the cockpit door and sat on him for about 20 minutes until the plane landed at Rick Husband Amarillo international airport at 10am. Shane Helton, 39, who was seeing off his son at Amarillo airport, said: "They pulled one guy out on a stretcher and put him in an ambulance." The flight had left New York around 7am and was in the air for three and a half hours before landing in Texas. The passengers completed their journey to Las Vegas several hours later on another flight. The FBI was co-ordinating an investigation with the police, the FAA and the Transportation Safety Administration, said FBI spokeswoman Lydia Maese in Dallas. She declined to comment on arrests. Earlier this month an American Airlines flight attendant took over the public address system on a flight bound for Chicago and spoke for 15 minutes about 9/11 and the safety of their plane, saying: "I'm not responsible for this plane crashing," passengers said. She was wrestled into a seat while the plane was grounded at Dallas-Fort Worth international airport. The attendant was taken to hospital. In 2008 an Air Canada co-pilot was forcibly removed from a Toronto to London flight, restrained and sedated after having a mental breakdown. A flight attendant with flying experience helped the pilot make an emergency landing in Ireland. None of the 146 passengers and nine crew members on board were injured. In August 2010 JetBlue flight attendant Steven Slater pulled the emergency chute on a flight from Pittsburgh after it landed at John F Kennedy international airport. He went on the public address system, swore at a passenger, grabbed a beer and slid down the tarmac. He was sentenced to probation, counselling and substance abuse treatment for attempted criminal mischief. An aviation expert remembered only two or three cases in 40 years where a pilot had become mentally incapacitated during a flight. John Cox, an aviation safety consultant and former airline pilot, said incidents in which pilots become mentally incapacitated during a flight were "pretty rare". He said he could only recall two or three other examples in the more than 40 years he has been following commercial aviation. Airlines and the FAA strongly encouraged pilots to assert themselves if they thought safety was being jeopardised, even if it meant contradicting a captain's orders, Cox said. Aviation safety experts had studied several cases where first officers deferred to more experienced captains with tragic results. In Tuesday's case the FAA is likely to review the unidentified captain's medical certificate, which must be renewed every six months to a year.