An airplane after taking off from Seville's San Pablo Airport Marcelo del Pozo / Reuters

On November 28, 2002, al-Qaeda-affiliated terrorists aimed two shoulder-fired missiles at an Israeli commercial airliner as it took off from the Moi International Airport in Mombasa, Kenya. Though both missed, the event marked the first missile attack on a civilian airliner outside of a conflict zone. Had the terrorists succeeded, all 271 civilians on the plane would very likely have been killed.

The weapon used, Man-Portable Air Defense Systems, or MANPADS, had first been developed in the 1940s as surface-to-air anti-aircraft missiles that could be fired by an individual or small group. By 2002 there were an estimated 750,000 around the world, some available on the black market for as little as $5,000. They had spread beyond war zones and now threatened civilians both physically and psychologically. U.S. Secretary of State Colin Powell warned of the weapons in October 2003: “No threat is more serious to aviation.”

Since then, ISIS may have replaced al-Qaeda as the world’s most prominent terrorist group, but the threat Powell identified remains just as serious. Russian officials now seem confident that a bomb brought down a Russian commercial flight over Egypt's Sinai peninsula, in an attack that was claimed by Sinai Province of the Islamic State, a group allegiant to ISIS. ISIS has also expressed interest in threatening the skies from the ground. In October 2014, the group released an online guide providing instructions for using shoulder-fired missiles to shoot down Apache helicopters: “Choosing the launching spot: Preferably somewhere high. ... The roof of a building or a hill with a solid surface to prevent the appearance of dust following launching.”

Terrorists’ abilities to acquire such missiles and launch them against U.S. targets have been a concern of American homeland-security agencies for more than a decade. In 2004, the Transportation Security Administration (TSA) led an effort to find out just how vulnerable American aviation was to shoulder-fired missiles, essentially by coordinating teams of FBI, Secret Service, and Defense Department representatives to think like terrorists. If someone, or a group of people, was going to launch an attack on a civilian airliner, how would they do it, and where? The teams focused initially on the largest and most highly trafficked airports within the United States—and a contingent of four people was assigned to New York’s John F. Kennedy International Airport and LaGuardia Airport.

They began by trying to internalize the motivations and goals of the hypothetical terrorist group, starting from the fundamental supposition that such a complex and consequential operation would not be attempted impulsively and without tremendous preparation. The most likely attackers would be rational and strategic actors with apparent political motivations. This initial insight helped narrow down the number of likely shooting zones. In theory, the area from which someone could hit a plane taking off, landing, or circling above a major airport with the widely available SA-7 missile is a few hundred square miles. For more advanced shoulder-fired missiles, such as the SA-18, that zone increases to a few thousand square miles. To zero in on areas that deserved the most focus, the team made four key assumptions about the most likely perpetrators.

The first was that the attackers would comprise a small multidisciplinary team, including a heavily armed security element to protect the shooter and a video element to capture the attack. Whoever actually pulled the trigger would be a uniquely valued and highly trained individual, probably with extensive combat experience, in addition to being smart and adaptable enough to enter the United States undetected. Subsequently, the terrorist organization would want the shooter to be safely extracted, and thus would conduct the shoot-down from an area near viable escape routes.

Second, given the political objectives of the terrorist groups most likely to conduct such an attack, they would not try to strike just any target of opportunity, but would likely aim for an Israeli or American domestic carrier rather than an airline affiliated with an Arab or Muslim country. Third, the attack would have to be planned, which meant that the group would conduct extensive surveillance of a given airport’s takeoff and landing patterns. This would necessitate that some members of the team survey the runways for weeks or months in advance, most likely from an area where they could do so undetected. Thus, if law enforcement was aware of a plot and wanted to seize the best opportunity to disrupt it in the planning stages, investigators would have to look for people observing those patterns over time from somewhere accessible, but not obvious.

Fourth, the TSA’s team assumed that the terrorists would shoot their missile at a plane as it took off, rather than as it began to land, since a plane taking off is burdened with tens of thousands of gallons of highly flammable jet fuel. This limits how quickly the plane can ascend, and also constrains its maneuverability, which would make it difficult for a pilot to turn around and land the plane at the same airport from which it took off if it were struck. And though it’s unlikely a strike would be accurate enough to hit the full fuel tank, flames could reach and ignite it. By contrast, if a plane was hit by a heat-seeking shoulder-fired missile as it was landing, the projectile would most likely strike near an engine, which the pilot could potentially adjust to and still land the plane with relative safety.

These four assumptions about how terrorists would likely think and behave limited the areas of focus, because the shooting zones were assumed to require a concealed location with an entrance and an exit that was within missile range of a plane taking off. It turned out that among the best and most likely shooting zones for JFK International Airport were the many cemeteries in Queens, which tend to occupy high ground and have few visual obstructions between them and the runways. For LaGuardia, a high-performance speedboat sitting in the open waters of Flushing Bay might be an attractive option, as would be the Trump golf course then under construction at Ferry Point in the Bronx.

The team’s work was used to inform and refine the crisis-response plan that would be activated if intelligence reporting indicated an active terrorist plot. The presumption was that the air-traffic controllers in the airport’s control tower would be able to roughly identify the origin of a missile launch from the smoke trail it left behind. The responding law-enforcement officers would then know, based upon the initial work of the assessment team, where exactly, given the missile’s estimated origin, a shooting team was likely to be located. Moreover, given that the team of attackers would likely be well-armed and trying to get the shooter out of the area, the responding officers would also expect to receive gunfire and would focus on the previously identified getaway routes.

These assessments were performed in the mid-2000s, but annual reviews have shown that the geography and physics of shooting a missile at a plane taking off have remained the same. The much greater concern today would be a MANPADS attack against a flight that originated overseas.

In the past 10 years, the TSA has led efforts to conduct similar assessments at the roughly 275 foreign airports representing the last point of departure for nonstop flights into the United States. Even so, the potential for such an attack on U.S. airports remains as real as it was in 2002, because thousands of portable missile systems remain in the hands of non-state actors. Moreover, shoot-downs of helicopters and transportation planes have increased in recent years, though, so far, only in overseas conflict zones such as Iraq, Somalia, Syria, and Egypt. During one four-month period in 2014, separatist rebels in Eastern Ukraine shot down 12 Ukrainian military aircraft with surface-to-air missiles even before the July 17 downing of Malaysia Airlines 17, which killed 298 passengers and crew. Those lethal missiles were fired mostly from sophisticated, radar-guided, self-propelled missile systems that probably could not be smuggled into the United States undetected.

Over the same period, new adversaries have risen to challenge America—organizations like ISIS and al-Qaeda in the Arabian Peninsula whose tactics and goals differ somewhat from those of core al-Qaeda. Yet their chosen weapons may be similar, which means that preventing an attack on U.S. commercial airliners—or worse, responding to one—will still require teams of law-enforcement and security personnel that can think like terrorists.

This article has been adapted from Micah Zenko's new book, Red Team: How to Succeed by Thinking Like the Enemy.

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