Reaching a gate for a commercial flight at a U.S. airport today typically demands a valid boarding pass, federal government security screening, and careful attention to the contents of carry-on luggage.
Air travel was not always so strictly regulated. In earlier decades, airlines used private contractors to operate security checkpoints. Full-sized shampoo bottles and cans of shaving cream were not confiscated for exceeding liquid limits, and friends and relatives could walk departing passengers straight to the gate to exchange goodbye hugs.
The screening procedures and security systems in place today were built layer by layer, often after attacks or foiled plots exposed fresh vulnerabilities—ranging from explosive devices hidden inside checked baggage to hijackers turning commercial airliners into weapons.
“Attacks on aviation have an impact much greater than attacks on anything else because aviation commands the attention of the world as the thing that links the world,” said Mary Schiavo, an aviation disaster attorney.
With the 25th anniversary of 9/11 approaching, here is how those tragic attacks, the earlier bombing of Pan Am Flight 103, and subsequent plots fundamentally reshaped airport and airline security.
The Lockerbie tragedy reshaped airport screening long before the September 11 attacks
Nearly 13 years before 9/11, a bomb destroyed an American commercial jet flying at 31,000 feet over Lockerbie, Scotland, killing 259 people on board and 11 on the ground. Investigators discovered an explosive hidden inside a radio-cassette player within a suitcase checked in Malta and transferred to Pan Am Flight 103 without a traveling passenger.
The Dec. 21, 1988, attack on the London-to-New York flight “stimulated the most significant changes in aviation security since the early 1970s,” former FAA Administrator Jane Garvey told the 9/11 Commission in 2003.
open image in galleryThe FAA instructed U.S. carriers at European and Middle Eastern airports to X-ray or manually inspect all checked luggage, execute extra random searches, and ensure checked bags belonged to boarded passengers.
Prompted by a presidential commission and Congressional legislation, the FAA posted security staff at major domestic and overseas hubs, arranged intelligence-sharing protocols, tightened cargo safeguards, instituted training criteria for private screeners, and researched blast mitigation and explosives-detection systems.
open image in galleryThe agency also conducted covert tests on airline and airport security by sending a specialized team “to simulate the criminal and terrorist attacker modus operandi,” Garvey testified. On Sept. 10, 2001, the FAA maintained that explosive devices represented the most dangerous hazard facing commercial aircraft and their passengers.
“The challenge is not formulating attack scenarios,” Garvey said. “The challenge is figuring out how best to allocate finite resources in an environment of uncertainty.”
The attempted terror attacks that led to shoe removal and the 3-1-1 liquid rule
Just over three months after September 11, 2001, Richard Reid, a British national, boarded American Airlines Flight 63 traveling from Paris to Miami with explosives concealed inside his footwear. He attempted to detonate the devices during the flight, but failed to ignite the fuse before passengers and flight crew successfully restrained him.
After the December 22, 2001 attempt, aviation officials initially encouraged travelers to voluntarily remove their shoes at checkpoints. Screening became compulsory five years later, coinciding with new restrictions placed on liquids and gels.
open image in galleryThose regulations were introduced after British investigators uncovered a conspiracy to detonate liquid explosives hidden inside drink containers on seven transatlantic flights. The plan involved assembling the weapons midair for suicide bombings, leading to the eventual conviction of six individuals.
In response, security personnel initially prohibited almost all liquids, gels, and aerosols beyond screening checkpoints. This complete ban was later adapted into the “3-1-1” policy, allowing travelers to carry small containers under 3.4 ounces in one clear, quart-sized bag.
By July 2025, the Trump administration officially rescinded the mandate requiring passengers to remove their shoes during airport security checks.
A Christmas Day terror plot paved the way for full-body scanners in every major airport
A Christmas Day plot in 2009 saw a passenger attempt to blow up Northwest Airlines Flight 253 as it drew near Detroit by igniting explosives concealed in his underwear. Though the device malfunctioned, it sparked a fire that left the traveler severely burned. The young man, Umar Farouk Abdulmutallab, who claimed to be an al-Qaida operative trained in Yemen, later admitted guilt to trying to destroy the plane.
open image in galleryStandard metal detectors at the time couldn’t detect plastic explosives beneath clothing. The TSA was already evaluating full-body scanners in select U.S. airports, and the near-miss prompted officials to accelerate deployment.
Utilizing radio waves, these scanners screen for a broad array of banned objects. Today, stepping into the booth with feet apart and hands raised is routine for most passengers.
The TSA is expanding facial scans and cockpit barriers in ongoing aviation security push
Security measures at U.S. airports continue to evolve, with the TSA expanding facial recognition technology to verify traveler identities. As of last month, newly built passenger aircraft must feature a retractable security gate between the cabin and the flight deck, protecting the cockpit when the reinforced main door is open. The Air Line Pilots Association is calling for secondary barriers on existing planes.
“Any one layer of security can be breached,” Jacobson said, “but collectively, when you put them on top of each other, what you end up with is a very resilient system.”