U.S. Central Command said that the U.S. military is investigating the possibility that a software problem in the Patriot Missile defense system may be responsible for targeting two friendly aircraft, but that other scenarios could just as likely be responsible for the mishaps."They're looking into a software problem. They're going to check everything out. When they do find a fault, they'll put it out to the rest of the world," said Navy Lt. Commander Charles Owens.On Sunday, a Patriot Missile battery on the Kuwait border accidentally shot down a British Royal Air Force (RAF) Tornado GR-4 aircraft that was returning from a mission over Iraq. Two British pilots were killed in the incident.Then on Monday a U.S. F-16 fighter jet fired at and destroyed a Patriot battery's radar dish after the pilot said the Patriot had 'locked on' to the plane.Published reports have linked the mishaps to software problems with the Patriot.A Washington Post story on Tuesday quoted unnamed Pentagon officials saying that the cause of the incidents was "obviously a software glitch."According to the Post, the crew of the Patriot battery had "taken cover" from incoming artillery shortly before the F-16 was locked on to by the Patriot, leaving the missile battery to operate "largely on automatic."A story on the Web site of Radio Australia also quotes an unnamed British Royal Air Force commander saying that a software "glitch" led to the accidental downing of the RAF plane.The software error caused the missile battery to read the RAF Tornado as an Iraqi missile, according to the Radio Australia report.In a briefing at U.S. Central Command in Doha, Qatar, on Thursday, however, General Vince Brooks, deputy director of operations, said that more needs to be known about the downing of the Tornado before the military makes a statement."We had the unfortunate incident with a Patriot Missile against a U.K. GR-4 aircraft. We will be truthful with you about it when we know some more, but right now, all reports are currently under investigation," Brooks said.In a briefing on Saturday, Major General Peter Wall said that the army checked its procedures for the Patriot following the incident and was "satisfied."Defense industry experts disagreed about the possibility of a software problem being solely responsible for downing a friendly aircraft."An operator has to lock on," said one industry expert who is familiar with the operation of the Patriot."If you're sitting in there, the radar is tracking everything in the sky. The operator moves a track ball, puts on one of the symbols, clicks on that and pulls up all the information -- speed, heading, altitude."That information, as well as an Identification Friend or Foe (IFF) beacon on the RAF plane would have identified it as a friendly aircraft and distinguished it from an incoming Iraqi missile, the expert said.Contrary to what the Post report said, the Patriot cannot function in an automated mode, the expert said."There's always a soldier, a man in the loop who makes the decision," he said.However, information on the Web page of Raytheon, the company that manufactures both the Patriot and its radar system indicates otherwise, listing "automated operations - including man-in-the-loop (human) override" as a "key feature" of the Patriot system.A likely scenario has problems with the Patriot's radar combining with human error to result in friendly fire, according to Victoria Samson, a research associate at the Center for Defense Information in Washington, D.C."A soldier at the radar might have seen something come in that didn't have a beacon and launched (a missile) before checking," Samson said.Recent operational testing of the latest Patriot Missile, the PAC-3, revealed software problems, Samson said.Experts agree that without hard information about the circumstances that preceded incidents on Sunday and Monday, theories on whether software, procedural or human error -- or some combination of those factors -- were to blame are pure speculation.But those who remember how claims about the Patriot's performance during the first Gulf War were later disputed say that it's reasonable to be skeptical of the claims made by Patriot boosters this time around."I hope (the Patriot Missile systems) are doing well. They're certainly vastly improved over the last ten years. Whether they're as reliable as their creators would like them to be? The jury's still out on that," Samson said.