At least two people were killed and 54 injured when a vintage aircraft ploughed into spectators at an air show in the US state of Nevada, officials and reports said. At least 12 victims were in critical condition after the crash in Reno, in which the World War II plane, piloted by a 74-year-old veteran of the show, smashed almost vertically down near a packed grandstand. Witnesses said the aircraft crashed into an area of boxes -- roped-off areas for spectators to relax while viewing the show -- while one said the pilot swerved to avoid even greater casualties if he had hit the grandstand itself. "It pretty well wiped out the front of the box area," said Mike Houghton, the head of the Reno Air Racing Association, declined to comment on how many people could have died, while giving the number of injured as 54. "We are all devastated by this tragedy," he added, briefing reporters. The aircraft was a World War II P-51 Mustang fighter, called the "Galloping Ghost." It was piloted by a Florida real estate developer, named as Jimmy Leeward, 74. Amateur video of the accident, shot from the grandstand, showed people gasping in horror as the plane ploughed almost vertically down into the tarmac. Reno Air Racing Association Mike Draper said the plane was a lap or two into the race when its pilot -- named as Jimmy Leeward, aged 80 -- called in a mayday. "We don't know why it crashed. The pilot did call in. He did pull out of the lap, which is what they do. They usually pull up, directly up to clear the race track," he added. Eyewitness Ben Cissell praised the pilot. "I think that that pilot in the last two seconds pulled up because he saw the bleachers and I would guess he probably saved 200 to 300 other people," he told CNN. Two people were confirmed dead at the Renown medical center, which said it was treating 23 of the injured, 11 of whom were in fair condition and 12 critical. The National Transportation Safety Board (NTSB) launched an immediate investigation, and would give updates on the number of dead in the accident, Houghton said. Cissell said he was only yards from the crash site, in the middle of the area of boxed-off sections with tables and chairs for spectators, divided off by velvet ropes. "I was about 100 feet from the crash site and I would think that the plane hit right at about the middle of those boxes," he said. "It’s just like a massacre. It’s like a bomb went off," said eyewitness Gerald Lent, quoted by the Reno Gazette-Journal. "There (were) people lying all over the runway." "One guy was cut in half. There’s blood everywhere... There’s arms and legs. One guy just said 'hey, there’s another foot over here," he added. Houghton dismissed suggestions that the health of the pilot -- initially reported to be 80 years old -- could have had a role in the crash. "All of his medical records and everything were up to date, spot on and Jimmy was a very experienced and talented, qualified pilot," he said, adding that he had been flying at the Reno air show since 1975.