A 25-year chain of attacks and foiled plots has shaped the modern U.S. airport checkpoint system, from the Lockerbie bombing and the post-9/11 creation of the TSA to shoe screening, liquids limits and full-body scanners. The layered model now used across commercial airports nationwide remains the core passenger experience for U.S. travel, reflecting each new threat as it emerged rather than one single overhaul.
The sequence began with Pan Am Flight 103 over Lockerbie in 1988, which exposed the risk of hidden explosives in checked baggage. After the 11 September 2001 attacks, Washington created the Transportation Security Administration and tightened screening across domestic and international routes. Richard Reid’s shoe-bomb attempt later that year led to voluntary shoe removal, which became mandatory in 2006. That same year, authorities moved to restrict liquids after a foiled transatlantic plot involving liquid explosives.
The attempted bombing of Northwest Airlines Flight 253 in 2009 then accelerated the deployment of advanced imaging scanners at U.S. checkpoints. Together, those changes built a layered security system led by the FAA, TSA and policymakers responding to repeated threats.