From hours at security to bulletproof cockpits: How 9/11 changed air travel

The terrorist attacks of September 11, 2001 — when hijacked airliners struck the World Trade Center and the Pentagon while a fourth crashed in Pennsylvania — prompted an immediate halt to much commercial air traffic and widespread airport closures. US airspace was grounded, and Canada closed its skies before reopening in stages: domestic flights resumed on September 12, international services on September 13, and remaining restrictions lifted the following day. The United States reopened its airspace on September 13.

Within weeks and months, governments moved to tighten pre-flight procedures. In November 2001 Congress passed the Aviation and Transportation Security Act, which established the TSA and required federal screening of all passengers and checked baggage. This marked a decisive shift from pre-2001 practices in which many domestic travellers could reach gates without showing identification and could be accompanied to departures by friends and family.

Airline operations and in‑flight protections were also strengthened. The Federal Air Marshal Service was expanded and laws were passed requiring cockpit doors to be reinforced and kept locked; some carriers such as Virgin announced reinforced doors as early as October 2001. Items that had once been permitted in carry-on luggage — including small knives and box cutters — were banned, and new measures such as shoe screening were introduced after an attempted shoe bombing in December 2001. In 2003 pilots could begin to be certified to carry firearms under the Federal Flight Deck Officer programme.

Security rules continued to evolve as new threats emerged. Following a foiled plot in 2006 to use liquid explosives, authorities limited liquids in carry-ons to containers of 100 millilitres or less and required them to be presented in clear bags. A failed attempt in 2009 to detonate an explosive hidden on a transatlantic flight accelerated installation of full-body scanners at many airports. From 2017, trials and wider adoption of biometric systems — including facial-recognition boarding trials — and stricter checks for larger electronic devices have further changed the passenger experience.

The cumulative effect of these measures has been longer processing times and more extensive screening. Research published in 2007 found that passenger-screening throughput at checkpoints had fallen from levels reported before the security changes, reflecting the additional time required for the layers of inspections and technology now standard at many airports.