More-detailed explanations are left to experts such as Theodore Postol, professor of science, technology, and national security policy at MIT, whose analyses more than a decade ago were the first to expose the Patriot’s poor performance in the Gulf War. Postol postulates that part of the problem with the Patriots that shot down the friendly planes in 2003 was electronic interference from nearby batteries. Each battery was aiming radar beams at the sky and calculating the altitude and range of airborne objects based on radar “returns.” But because of their close proximity to each other, some batteries might have picked up radar signals originally sent by other batteries.
The result might have been the generation of false targets, and the correlation of those false targets with actual aircraft in the vicinity. The Patriot crews would then conclude they were looking not at a friendly plane but rather at a missile. Pike says the army failed to anticipate how multiple batteries could create such conflicts. “When [the U.S. Army] got into combat, they employed it in ways they had not trained for in peacetime. They had never planned on having this many Patriot batteries operating together in such close proximity with other radars,” he says. The second obvious technological problem, in Postol’s view, was the homing device in the Patriot interceptor itself. Once a missile was launched, it should have been searching for targets only in a limited area. But two of the missiles that targeted friendly planes made significant course corrections in order to reach the jets, he says. “So there is something wrong with the lock-on and homing of the missile,” Postol says, “because in two cases they locked on to targets that were on trajectories far different than the targets they thought they were shooting at.”
Philip Coyle, who during the Clinton administration was an assistant secretary of defense and director of operational test and evaluation, is now senior advisor to the Center for Defense Information, a think tank in Washington, DC. He believes that the Patriot’s Achilles’ heel is clearly its software. “One of the lessons is that the devil is in the details with respect to software,” he says. “You really have to understand how these computers and software work – and I don’t think that Raytheon has [done so].” He adds that, since military equipment grows more networked and automated every year, and thus more dependent on software, solving the Patriot’s problems could be crucial to the future of warfare.
While Raytheon would not provide interviews about the Patriot’s misidentification of friendly planes, in an e-mail, company spokesman Guy Shields emphasized problems outside Raytheon’s walls. “Two of the main shortfalls seen in  transcend just the Patriot; they involve combat identification and situational awareness,” he wrote, citing the Defense Science Board report. “The Army has taken action, but only they can talk about it,” Shields added.
To Postol, though, what’s lacking is a critical examination of the continual failures that dog the Patriot program. “If the organization doesn’t set a goal of identifying and fixing problems, they don’t get fixed,” Postol says. But if he’s right about what happened in 2003, fixing problems with automated weapons systems will require more than openness. It will require those who design and implement the systems to worry more about what can go wrong in a combat zone.