Terrorism Summary

  • Last updated on November 10, 2022

The use of force or violence to achieve political goals through coercion and fear.

Terrorism and Commercial Aviation

Since the 1960’s, commercial aircraft have been a favorite target of terrorists, for several reasons. One explanation emphasizes the political nature of terrorism, because airliners serve as symbols of their countries of origin. For example, in the mind of a terrorist, an attack on an American Airlines aircraft, anywhere in the world, is an attack on the United States. Airliners are usually filled with influential citizens of the country that sponsors the airline.

Additionally, in cases of aircraft hijacking, sometimes called skyjacking, any passengers on board the airplane who are not natives to the airline’s country of origin provide a bonus in that their home nations will doubtless bring pressure upon the target country to satisfy the terrorist’s demands.

Another reason for the popularity of airliners as terrorist targets is a tactical one. As bombing targets, commercial aircraft, incredibly complex machines operating at blinding speeds and altitudes, are distressingly vulnerable to even small explosive charges. In hijacking situations, airliners amount to self-contained, highly mobile vehicles capable of transporting hostages anywhere in the world, including to nations that may be sympathetic to the hijackers. The planes themselves can also be used as weapons.

Lastly, airliners make attractive terrorist targets because of the ultimate purpose of terrorism itself: to introduce widespread fear and insecurity. Terrorists are always weaker in numbers and arms than the entity against which they struggle. Their deficiencies do not allow them simply to declare war and settle their differences on the battlefield. Terrorism provides this weaker group with the means to magnify their power through hit-and-run attacks against a defenseless population, protected only by a government the terrorists hope will be exhausted in its futile effort and, eventually, give in to the terrorists’ demands. Because many people harbor a fear of flying under the most ideal conditions, the specter of terrorist hijackings and bombings only exaggerates their concerns, further magnifying the terrorists’ advantage.

Nonterrorist Commercial Hijackings

Since the early 1950’s, commercial air carriers have been routinely commandeered by passengers. At that time, the hijacking of airplanes was a novel and daring means by which individuals or small bands of people fled Eastern European Soviet Bloc nations. To escape these communist countries, hijackers would produce weapons and seize control of an airplane flying a domestic route, divert it to a free country in the West, and deplane to seek political asylum, leaving the aircraft free to return.

During the early 1960’s, another round of hijackings was initiated in the United States by Cuban expatriates who had fled their homeland during the Cuban Revolution. Homesick, unhappy with life in their adopted country, and hoping to ingratiate themselves with the communist regime by foiling the United States, they would hijack domestic U.S. air flights and divert them to Havana. Similar hijackings began to occur after the Mariel boat lift of 1980, when disgruntled Cuban expatriates employed them to return to Cuba.

In all these cases, the hijackers made no demands other than transportation to a place otherwise inaccessible to them. Because they would seize any aircraft capable of making the trip regardless of national origin, none of these hijackings can truly be regarded as terrorism.

One further category of nonterrorist hijackings began to occur during the early 1970’s. A man calling himself Dan Cooper, erroneously reported by the press as D. B. Cooper, boarded a Northwest Airlines 727 flight from Portland, Oregon, to Seattle, Washington. In the air, he passed a note to a flight attendant that claimed he had a bomb in his briefcase. He demanded $200,000 and four parachutes, apparently wishing to suggest that he might force crew members to jump with him and thus ensure that the parachutes would be serviceable.

The airline quickly capitulated, and the flight crew landed the aircraft in Seattle. After receiving the money and parachutes, Cooper allowed the passengers to leave while retaining the flight crew. He then instructed the pilot to fly a course to Reno, Nevada. While over the wilds of Washington, he opened a rear door of the plane and leaped into the teeth of a below-zero storm. He was never seen again, although several thousand dollars of the ransom washed ashore in a Columbia River tributary nine years later. Cooper’s hijacking and the twenty-seven copycat attempts that soon followed all amounted to spectacular robberies more than to acts of terrorism. The perpetrators made no demands other than for money.

Terrorist Commercial Hijackings

On July 22, 1968, an event occurred that would revolutionize both terrorism and commercial air travel. Three members of the Popular Front for the Liberation of Palestine, (PFLP), a splinter group of the Palestine Liberation Organization (PLO), seized control of a Boeing 707 flying a route from Rome, Italy, to Tel Aviv, Israel. The airplane was operated by El Al, the national airline of Israel.

The hijackers ordered the flight to Algiers, where Algerian troops guarded the Israeli hostages after releasing the non-Israelis. They held the victims captive for more than one month, until Israel released sixteen Arab prisoners in satisfaction of the hijackers’ demand.

For the first time in history, terrorists had carefully targeted a particular country’s national air carrier, and the passengers on board, for political effect. By placing so many people into mortal jeopardy, they had forced an antagonistic state to bargain with them, despite Israel’s prior disdain, and they internationalized their struggle by turning it into a major media event.

With the creation of the state of Israel by the United Nations in 1948 and the series of wars between Arabs and Israelis that followed, more than one million Palestinians were dispossessed from their former homes. Mostly living in squalid refugee camps in neighboring Arab countries, the Palestinians desperately sought support for a return to what they considered their rightful homes. However, few people, particularly those in the West, paid much attention to their struggle. After twenty years of frustration and despair, some of these Palestinians began to execute raids across the border into Israel. Still, few people outside of the area took notice, and fewer offered support.

The 1968 El Al hijacking put the PFLP’s cause on the front page of virtually every newspaper. Dr. Georges Habash, leader of the PFLP, remarked that “When we hijack a plane it has more effect than if we killed a hundred Israelis in battle. For decades world opinion has been neither for nor against the Palestinians. It simply ignored us. At least the world is talking about us now.” The Palestinians surely realized that they would be roundly condemned for this act and for others over the next few years, but they believed it imperative first to capture the world’s attention and later to rehabilitate their image.

Terrorists read the newspapers, and they are intelligent people. Almost immediately, groups everywhere began to imitate this victorious stunt, a phenomenon sometimes called the copycat effect. The Israelis learned a lesson, too, and instituted what are probably the most thorough airline security measures in the world.

Although political hijackings flourished worldwide over the next two years, no group seized planes more regularly or to greater effect than the PFLP. In 1970, the PFLP orchestrated probably the most ambitious terrorist hijacking operation of that period. On September 6, 1970, teams of PFLP terrorists simultaneously hijacked three aircraft, with a further attempt at a fourth.

The one failed attempt involved another El Al flight out of Tel Aviv, Israel. Two PFLP agents, one of them a woman, pulled handguns and hand grenades in midflight but were overcome by Israeli sky marshals with the help of passengers. The three other attempts proved stunningly successful. A Pan Am 747 flying out of Zagreb, Yugoslavia, was diverted to Cairo, Egypt, where the terrorists released the passengers and crew before they exploded the plane.

Parallel to this incident, other PFLP teams hijacked a Trans World Airlines (TWA) flight out of Frankfurt, Germany, and a Swissair flight out of Zurich, Switzerland, diverting both to an abandoned World War II-era British landing field in Zerka, Jordan. Hostages on board the airplane came from many countries, creating a negotiating nightmare for the victims’ representatives but giving the terrorists tremendous leverage in bargaining for the release of imprisoned comrades. After weeks of discussion, the parties struck a deal freeing the hostages, with PFLP explosives experts punctuating the end of the ordeal by exploding the airplanes while news cameras rolled.

Although the PFLP’s impetuous plan was a stunning coup that garnered invaluable publicity for the Palestinian movement, the PLO paid a price, because it had not cleared this operation with King Hussein of Jordan. The widespread condemnation resulting from the mass hijackings caused Hussein to reassess the wisdom of hosting what was turning into a highly armed, uncontrollable state-within-a-state. He ordered his army forcibly to expel the Palestinians. After fierce fighting, resulting in far more casualties than the Israelis had managed to inflict in twenty years of combat, the Jordanians swept the PLO out of their country. Familiar with relocation, the PLO settled in Lebanon.

The consequences of the PLO’s expulsion were not long in coming. A new terrorist group surfaced, probably the most ruthless of all the groups under the PLO umbrella. This new group defiantly called itself Black September, after the month in which the PLO was evicted from Jordan. The Black September group is best known for two terrorist operations that occurred at airports rather than in flight.

The first, on May 30, 1972, involved three Japanese Red Army terrorists on contract to Black September who infiltrated the Lod Airport terminal in Israel. Because the strict Israeli security measures adopted after the 1968 hijacking would surely have prevented them from carrying weapons on board a flight, they simply fired their submachine guns and threw grenades into a crowd of deplaning passengers. Twenty-eight people were killed and another seventy-six were injured before Israeli airport security police killed two of the terrorists and captured the other.

Commercial aviation also played a peripheral role in what is one of the most compelling, publicity-grabbing terrorist operations of all time. The stage for this drama was the 1972 Olympic Games held in Munich, West Germany, which was eager to establish itself as a modernized country and to atone for the damage of World War II, particularly with respect to the Jewish victimization of the Holocaust. On September 5, eight Black Septembrists invaded the Israeli barracks at the Olympic village, killing two athletes and taking hostage the surviving nine Israeli team members.

The terrorists demanded the release of several members of Germany’s Baader-Meinhof gang from prison, along with 236 Arab terrorists held in Israeli prisons. Israel was determined to take a hard-line approach to discourage future terrorist acts. After days of fruitless negotiations, the Germans laid an ambush. The terrorists and their hostages were helicoptered to a local military airport, where German police snipers opened fire. The terrorists, however, managed to kill all nine hostages with grenades and submachine-gun fire before they were captured or killed. Because of the great attention already attendant to the Olympic Games, people worldwide were riveted to this drama through its tragic conclusion.

The fact that both of the Black September terrorist operations involved airports rather than flights in progress is no coincidence. While commercial aviation remained as attractive to hijackers as ever, airline security staff was working feverishly to defeat the hijackers’ tactics. Shortly after the Cooper hijacking, U.S. airports began searching carry-on luggage and boarding passengers through metal detectors. From a high of more than 150 terrorist and criminal hijackings worldwide in the two years from 1968 to 1970, the number of attempts dropped to about one-third that number in the years from 1971 to 1973 and by nearly another one-third in the years from 1974 to 1976. Purely terrorist hijackings dropped by nearly one-half during that time, a smaller reduction that probably reflects the intense motivation and greater resources of terrorists compared to other hijackers.

Terrorist Bombings

Although the act of hijacking airliners is popular with terrorists, the act of taking hostages carries serious disadvantages. Terrorists risk imprisonment if they surrender and death at the hands of counterterrorist forces if they do not. Because only the most committed terrorists would embark upon such risky missions, the use of bombs increased. Although a successful midair bombing denies terrorists the bargaining advantage of an airplane full of hostages, the dramatic impact and the specter of fear that such an act engenders within the traveling public are significant motivators.

Assuming that the bomber can manage to plant the weapon aboard the aircraft or dupe some innocent passenger into carrying it aboard, the risk to the terrorist is minimal. Another advantage is that, if the bomb can be timed to detonate over deep ocean waters, any incriminating evidence is virtually guaranteed to be unrecoverable.

The most prominent example of a terrorist bombing of a commercial airliner involved the crash of Pan Am Flight 103 over Lockerbie, Scotland, on December 21, 1988. The aircraft was a Boeing 747 en route to New York from Frankfurt, Germany, with a stop in London, England. All 259 people aboard the plane died as well as eleven more on the ground. A painstaking investigation concluded that Semtex plastic explosive concealed inside a radio stowed with checked luggage provided the blast that ruptured the baggage compartment, bringing about a catastrophic breakup of the aircraft. In 2001, two Libyan men were brought to trial in Scotland for the murders. The court acquitted one of the defendants and convicted the other, sentencing him to a twenty-five-year prison term.

Of particular concern is the new bombing technology, using sophisticated explosives and triggering mechanisms, in the hands of increasingly fanatical terrorists. For example, in 1996, a federal jury convicted three Middle Eastern men, including the mastermind of the 1993 World Trade Center bombing, for conspiring to blow up a dozen U.S. airliners, with an estimated four thousand victims, in a two-day spree of terrorism designed to punish the United States for its support of Israel. A chance fire in a Manila, Philippines, apartment rented to one of the men alerted police to suspicious materials and exposed the plot before the terrorists could complete their preparations.

The terrorists’ plan was to smuggle powerful bombs using liquid nitroglycerin stabilized with cotton into contact-lens solution bottles hooked to timers built from rewired digital watches and 9-volt batteries. They intended to board flights with multiple legs and deplane at the first stop while leaving behind their carry-on luggage containing the bombs set to go off after the planes had again taken off.

Although new types of bombs are difficult to detect with existing airport security measures, new defenses are being developed. Because most bombs smuggled aboard aircraft are relatively low-powered, engineering efforts are being put forth to harden the luggage compartments against explosions. Efforts are underway to perfect and deploy explosive-detection systems using computed tomography technology to screen checked baggage; trace detectors to screen electronics, such as laptop computers and cell phones; and canine teams to screen luggage and vehicles visiting airports. Even with these efforts underway, however, most experts regard bombing as the most serious continued terrorist threat to commercial aviation.

Aircraft as Terrorist Weapons

Terrorists can also use aircraft as tools to commit terrorist acts. Although lacking the political goal needed to qualify as a true terrorist mission, one incident came close to succeeding on September 11, 1994, when a thirty-eight-year-old man named Frank Corder, after drinking alcohol and smoking crack cocaine, stole a Cessna 150 from a small airport in Maryland. He was not a licensed pilot but had received sufficient instruction for solo flight. Corder took off and flew southwest to Washington, D.C., where an accident reconstruction shows he deliberately dove the plane at the White House, crashing on the lawn just south of the building and sliding into its corner. Fortunately, the First Family was staying elsewhere at the time because the residence was undergoing renovation work. Corder had earlier told friends that he wished to commit a dramatic suicide by flying a plane into either the White House or the Capitol Building. Although his motive suggests drunken dementia more than terrorism, genuine terrorists can concoct a similar plan as an act of political defiance.

On the morning of September 11, 2001, in what was immediately termed the worst act of terrorism in history, four commercial jetliners were hijacked and three of them were crashed into significant American buildings. Two airplanes hit New York City’s World Trade Center, collapsing both of the center’s Twin Towers. Another crashed into the Pentagon, in Washington, D.C., collapsing part of that building. A fourth airplane crashed outside of Pittsburgh, Pennsylvania, when the passengers learned of the other hijackings by phone and confronted the terrorists. Many believed that the White House or the Capitol Building was the intended target.

Although no terrorist group immediately claimed responsibility for the crashes, it soon became clear that the terrorists were Islamic fundamentalists from the al-Qaeda network run by Saudi billionaire Osama bin Laden out of Afghanistan. It was the same group that had bombed the World Trade Center in 1993. In the weeks that followed, bin Laden threatened further terrorist acts against Americans and made such demands as the withdrawal of all Western troops from the Middle East and justice for Palestinians.

The hijackings exposed serious lapses in security. There were four teams of terrorists, nineteen men in all—two of whom were on a Federal Bureau of Investigation (FBI) watchlist. The hijackers smuggled box cutters and other knifelike instruments onto the planes. They gained relatively easy access to the cockpits, either killed or incapacitated the flight crews, switched off the transponders, and took over the controls. These acts also revealed the escalation of air terrorism. Because the hijackers were on a suicide mission, they did not need to worry about planting bombs, negotiating demands, or releasing hostages. Conventional wisdom about complying with the hijackers was useless.

Furthermore, especially in comparison to most hijackings, the plan was complex. Several of the hijackers had received sufficient training at aviation schools in Florida to control the jets in flight. (Such training solved a problem experienced in a similar attack by the al-Qaeda network in 1994, which failed in its objective of crashing into the Eiffel Tower because the pilot of the hijacked Air France jet did not cooperate and the terrorists could not fly the plane.) All four flights were scheduled to depart at roughly the same time. The hijackers chose Tuesday, a slow day of the week, to minimize the number of people on board and the odds of resistance. They claimed to carry explosives in order to control the passengers. (Ironically, one team failed because the hijackers apparently saw no harm in passengers calling people on the outside.)

The terrorists boarded flights at three different airports—Boston’s Logan Airport, Washington’s Dulles International Airport, and Newark International Airport in New Jersey—that were known to be lax in their screening procedures. They chose large jets, 767’s and 757’s, en route to California and thus carrying large amounts of highly flammable jet fuel to create mass destruction. They selected planes from the top air carriers in the United States, two from American Airlines and two from United Air Lines. They chose targets symbolic of the country’s military and economic power. In the course of a few hours, they caused the deaths of more than three thousand people on the planes and on the ground. Most of all, the terrorists succeeded in striking fear in the hearts of Americans, many of whom had believed their country to be safe from such acts.

Not much imagination is needed to construct other scenarios using aircraft to carry out spectacular terrorist operations. Yet surprisingly, few of these incidents have been recorded. Some have been planned but, for various reasons, did not come to fruition. An explanation for this lack of initiative, perhaps, is that most terrorists do not have access to tools as sophisticated as high-performance aircraft or the training to operate them. Terrorists are still more likely to deliver bombs by hand than by airplane.

  • Hoffman, Bruce. Inside Terrorism. New York: Columbia University Press, 1998. A thorough examination of selected topics.
  • Jenkins, Brian Michael. “Terrorist Threat to Commercial Aviation.” IDF Journal, Fall, 1989. An insightful article on the threats of hijacking and bombing.
  • Katz, Samuel M. Guards Without Frontiers. London: Arms and Armour Press, 1990. A good treatment of Israel’s struggle to protect itself against terrorist acts.
  • Poland, James M. Understanding Terrorism. Englewood Cliffs, N.J.: Prentice Hall, 1988. A well-written overview of terrorism.

Accident investigation

Airline industry, U.S.

Airport security

American Airlines

El Al

Emergency procedures


National Transportation Safety Board

Pan Am World Airways

Safety issues

Trans World Airlines

United Air Lines

The use of a hijacked commercial airplane as a missile to attack the Pentagon inWashington, D.C. on September 11, 2001, was both a literal and a symbolic terrorist blow to the security of the United States.

(AP/Wide World Photos)
Categories: History