6 Ways Travel Has Changed From Small Knives To Facial Recognition

Airport Screening Shifted From Airlines To The Federal Government

Back in 2001, the Federal Aviation Administration (FAA) set aviation security rules, but airlines were responsible for implementing passenger checkpoint screening, generally through private contractors.

When the 9/11 Commission’s final report found serious weaknesses across the security system, a change came rapidly. Only about two months later, in November 2001, Congress passed the Aviation and Transportation Security Act and established the Transportation Security Administration (TSA).

In a 2021 congressional hearing marking TSA’s 20th anniversary, current and former agency leaders described how screening had evolved from a largely one-size-fits-all system centered on metal detectors and X-ray machines to a risk-based approach, passenger vetting through Secure Flight and more advanced detection technology.

Today, security has multiple layers, including federal or federally overseen screeners, explosives specialists, canine teams, intelligence-driven procedures and technology ranging from state-of-the-art imaging to computed tomography scanners.

Security Screening Now Begins Before Travelers Reach The Airport

TSA’s Secure Flight program, implemented after 9/11, compares passenger information with federal government watchlists before travelers reach the security checkpoint. It applies to flights within, into, out of and over the United States.

The contrast with 2001 is substantial. CAPPS, a screening system used pre-9/11, was already attempting to identify potentially higher-risk passengers, but additional scrutiny generally focused on their checked baggage rather than their person or carry-on.

For example, in 2001, FAA guidelines prohibited knives with blades four inches or longer, while the industry checkpoint guide expressly permitted pocket utility knives with blades under four inches.

According to the 9/11 Commission report, the aviation system at the time was more focused on sabotage and explosives than a suicide hijacking.

Investigators found that knives were seen aboard all four hijacked aircraft, while evidence also indicated that these were ‘permitted’ knives with blades under four inches.

The Commission also found that more than half of the 19 hijackers were flagged for further inspection, yet the consequence applied only to their checked luggage and not their carry-on.

Today, knives, with limited exceptions such as plastic or round-bladed butter knives, are prohibited in carry-ons under current TSA rules.

Airport Security Became More Risk-Based, Not Just More Restrictive

Post-9/11 security also created a faster path for travelers considered lower risk.

TSA PreCheck began as a pilot program in 2011, while the application-based program was formally introduced in December 2013.

Applicants, U.S. citizens, U.S. nationals and lawful permanent residents, voluntarily provide biographic and biometric information for a security threat assessment before receiving expedited screening eligibility.

For eligible travelers, TSA PreCheck can mean using dedicated security lanes and avoiding some of the procedures associated with standard screening. It is a broader shift from a largely one-size-fits-all checkpoint toward risk-based security.

Americans Could Once Return Home Without A Passport

Perhaps the most surprising change for American travelers happened at the border rather than the airport.

Before the Western Hemisphere Travel Initiative, U.S. and Canadian citizens entering the United States from within the Western Hemisphere faced no standardized documentary requirement.

This meant that pre-9/11 travelers could use numerous forms of documentation or, in some circumstances, an oral declaration of citizenship was sufficient.

Since June 1, 2009, when the land-and-sea requirements of the Western Hemisphere Travel Initiative took effect, U.S. citizens returning by land or sea from destinations such as Canada and Mexico have to present a passport or another approved secure document.

Foreign Visitors Are Now Vetted Before They Fly To The U.S.

The Electronic System for Travel Authorization (ESTA), which became mandatory in 2009, allows the U.S. government to assess travelers in the Visa Waiver Program before boarding any flight bound for the U.S, rather than only when arriving at the U.S. border.

The arrival process has also become increasingly biometric. As of July 17, 2026, U.S. Customs and Border Protection says it uses facial biometric comparison to process travelers entering the country at 238 airports.

Security Is Stricter, But Not All Rules Stay Forever

Before 9/11, passengers did not routinely remove their shoes at U.S. airport security. That changed in the post-9/11 era, after Richard Reid attempted to detonate explosives hidden in his shoes in December 2001.

Since August 2006, TSA has required most passengers to remove their shoes for X-ray screening. It is a rule that remained in place for nearly 19 years before TSA revoked it nationwide in July 2025.

Identity checks have also become more automated. Instead of relying mainly on an officer to visually inspect an ID and boarding pass, newer TSA systems can electronically authenticate the ID and confirm the passenger’s reservation and screening status.

All liquids and gels were banned in carry-on as of August 10, 2026. While the 3-1-1 liquids rule introduced in September 2006 remains in place today, at airports equipped with CT scanners, passengers may be able to leave laptops and travel-size liquids in their carry-ons.