Politics
To travel on a commercial flight from a U.S. airport, passengers generally need a boarding pass before they can proceed to the gate.
To travel on a commercial flight from a U.S. airport, passengers generally need a boarding pass before they can proceed to the gate. They must then go through security screening overseen by the federal government, with particular attention paid to items in their carry-on luggage. But it was not always this way. There was a time when passengers went through security checkpoints staffed by private contractors selected by the airlines. Large bottles of shampoo or cans of shaving cream were not confiscated for exceeding the permitted limits on liquids. Friends and family members could accompany departing passengers all the way to the boarding gate and even hug them goodbye before the flight.
The security system and screening procedures that air travelers face today have gradually developed over time. Changes were introduced whenever an attack or attempted attack exposed new security vulnerability—sometimes in the form of a bomb hidden in luggage, and sometimes involving hijackers who turned the aircraft itself into a weapon. According to aviation disaster attorney Mary Schiavo, attacks on aviation have a far greater impact than attacks on almost anything else because the world’s attention is focused on air travel, which connects people around the globe.
As the 25th anniversary of the September 11 terrorist attacks approaches, this review examines how those attacks, the bombing of Pan Am Flight 103 before them, and terrorist plots that emerged later changed security at airlines and airports.
No single day changed air travel more than September 11, 2001. On that day, 19 al-Qaeda hijackers seized four commercial airplanes. Two of the planes crashed into New York’s World Trade Center, one struck the Pentagon, while the fourth crashed into a field in Pennsylvania. Mary Schiavo, who served as the U.S. Department of Transportation’s Inspector General from 1990 to 1996, said that before 9/11, authorities generally believed that hijackers would negotiate to achieve their demands and would not deliberately destroy an aircraft as part of an attack strategy.
“At the time, there was generally no focus on suicide attackers,” she said. The Federal Aviation Administration (FAA) immediately restricted access to airport gates to ticketed passengers only and banned knives and box cutters from carry-on luggage. The 9/11 hijackers had used small knives to threaten passengers, attack crew members and take control of the aircraft.
The U.S. Congress established the Transportation Security Administration (TSA), transferring responsibility for screening passengers, baggage and other cargo to federal government employees. Under legislation passed in November 2001, cockpit doors were required to be reinforced, additional federal air marshals were deployed on flights, and all checked baggage was required to be screened for explosives.
Nearly 13 years before 9/11, a bomb exploded aboard an American airline’s jumbo jet while it was flying at an altitude of 31,000 feet over Lockerbie, Scotland, destroying the aircraft. All 259 people on board and 11 people on the ground were killed. Investigators found that the explosive device had been hidden inside a radio-cassette player, which was placed inside a suitcase checked in at Malta. The suitcase was later transferred onto Pan Am Flight 103, even though no passenger was traveling with the luggage.
The attack on the London-to-New York flight on December 21, 1988, led to major changes in aviation security, considered the most significant since the early 1970s. Following the attack, the FAA ordered U.S. airlines operating at airports in Europe and the Middle East to screen or physically inspect all checked baggage, conduct additional and random searches, and verify that checked luggage belonged to a passenger who was traveling on the flight.
Three months and 11 days after the 9/11 attacks, Richard Reid boarded American Airlines Flight 63 from Paris to Miami with explosives hidden inside his shoes. The British national attempted to detonate the explosives during the flight but failed to ignite the fuse. Other passengers and crew members eventually restrained him. Following the incident on December 22, 2001, the TSA and airlines began asking passengers to voluntarily remove their shoes during security screening. Less than five years later, removing shoes became mandatory.
These changes came after British authorities announced that they had foiled a plot to destroy seven transatlantic passenger flights using liquid explosives concealed in beverage bottles. According to authorities, the plotters planned to assemble the devices aboard the aircraft and detonate them in midair as suicide attacks. Ultimately, six people were convicted in connection with the plot. The TSA immediately banned passengers from carrying almost all liquids, gels and aerosols through security checkpoints. The blanket ban was soon replaced by the “3-1-1” rule. Under the rule, passengers may carry liquid containers containing 3.4 ounces (100 milliliters) or less, and all containers must be placed in a single clear, quart-sized plastic bag.
In July 2025, the Trump administration ended the shoe-screening requirement that had required passengers to walk barefoot or in just their socks while going through airport security. On December 25, 2009, a passenger aboard Northwest Airlines Flight 253 attempted to detonate explosives concealed in his underwear as the aircraft approached Detroit. The device failed to explode, but it caught fire, severely burning the passenger. The young man, Umar Farouk Abdulmutallab, claimed to be a member of al-Qaeda and said he had received training in Yemen. He later pleaded guilty to attempting to destroy the aircraft.
The conventional metal detectors used at the time could not detect the plastic explosives hidden beneath Abdulmutallab’s clothing. The TSA had already been testing full-body scanners at some U.S. airports, but the incident prompted authorities to accelerate the deployment and use of the technology. These radio-wave scanners can detect various types of prohibited items. Today, for most passengers, standing inside the scanner with both feet slightly apart and their hands raised above their heads has become a routine part of the security screening process.
Security screening at U.S. airports continues to evolve. The TSA is expanding the use of facial-recognition technology to verify passengers’ identities. As of last month, newly manufactured passenger aircraft are required to have an additional retractable security barrier between the cabin and the flight deck. The barrier is designed to protect the cockpit when the main reinforced door is open. The Air Line Pilots Association wants these additional security barriers to be installed on aircraft already in service as well.
