The Patriot antimissile system, hailed by U.S. officials as one of the high-tech success stories of the Iraq war, also inflicted some of the most damaging "friendly fire" of the conflict.
The Defense Department has acknowledged that the antimissile system was involved in the downing of two allied warplanes, resulting in the deaths of three airmen. The two aircraft -- one American and one British -- are the only confirmed cases of planes being shot down during the war. Another plane narrowly escaped becoming the third victim of the Patriot system.
"The Patriot should have been stood down until they figured out why it was shooting down planes," said Joseph Cirincione, who directed a congressional assessment of the Patriot after the 1991 Persian Gulf War. "It's bad enough that it happened once. It's unconscionable that it happened again."
The sophisticated ground-based antimissile system rocketed to prominence in the 1991 Gulf War, gaining the nickname "Scudbuster" as it seemed to obliterate Iraqi long-range ballistic missiles heading for Tel Aviv and Riyadh. But after the war, congressional and independent analyses concluded that the Patriot may actually have missed every Scud it targeted.
Now, the friendly-fire incidents in the current campaign have raised concerns that the long-troubled system is still too complex and poorly tested to be deployed.
The military maintains that the system is vastly improved since 1991. It has spent $3 billion on the Patriot's missile and tracking technologies, and, during the current campaign, U.S. Central Command in Qatar said the system destroyed all nine Iraqi missiles it targeted.
"We are well along in our goal of demonstrating its reliability," Lt. Gen. Ronald Kadish, director of the Pentagon's Missile Defense Agency, told a Senate Appropriations Committee panel April 9. He called the Patriot's overall performance "very good."
But at the same hearing Kadish acknowledged there could be lingering problems. When asked whether the downing of the two allied jets and the near-shooting of another were caused by human or mechanical error, Kadish said, "I think it may be both."
He added, "There are investigations underway into each of the three incidents. I think we should wait until they're complete before we begin jumping to conclusions as to where the fault lies."
The Patriot attacks on allied planes were particularly puzzling given that throughout the war, no Iraqi aircraft were aloft.
"Why were the Patriots even shooting at aircraft?" asked Philip Coyle, former assistant secretary of Defense and director of operational testing and evaluation for the Pentagon. "We ruled the skies in Iraq, so almost by definition any aircraft up there was either ours or British."
The Patriot system, designed in the 1970s to shoot down enemy aircraft, should have been able to distinguish between relatively slow-moving planes and speedy rockets fired by Iraqi forces, Coyle said.
"If they can't tell the difference between a missile and an airplane, then they need much more restrictive rules of engagement," he said.
The first friendly-fire incident occurred March 23, when a British Tornado GR4 fighter-bomber was shot down by a Patriot battery protecting an airfield in northern Kuwait. Flight Lts. Kevin Barry Main and David Rhys Williams were killed.
A week and a half later, according to Central Command spokesman Lt. Herb Josey, a U.S. Navy F/A-18C Hornet was shot down by a Patriot missile over central Iraq, killing the pilot, Lt. Nathan D. White.
On March 24, a Patriot battery locked its radar on a U.S. Air Force F-16 Falcon in preparation for firing a missile. The plane's pilot, flying about 30 miles south of the Iraqi city of Najaf, averted disaster by firing first, disabling the battery with a radar-seeking missile. No U.S. soldiers were injured in the incident.
"The F-16 pilot probably knew he was being painted by a ground surface-to-air missile radar, but he may not have known it was a Patriot. He may have thought it was an Iraqi SAM," Coyle said. "The F-16 pilot did the right thing."
Experts said that such friendly-fire episodes stem from the long-range, split-second nature of modern war. A compounding factor is the enormous complexity of the Patriot system, which makes it vulnerable to mechanical, computer and human error.
The Pentagon will look closely at the Patriot's automated engagement mode, in which the system's radar may lock onto a target without operator intervention, as a possible culprit, Coyle said.
At the Senate hearing, Kadish said that possible system defects or a breakdown of the "identification friend or foe" system -- a primary way to identify aircraft in battle -- also will be scrutinized.