25 years later, 9/11 still shapes the way we fly. Here's how air travel changed after the attacks.

A TSA security checkpoint at John Wayne Airport in Santa Ana, California. Jeff Gritchen/MediaNews Group/Orange County Register via Getty Images Aviation security was completely overhauled after the terrorist attacks of September 11, 2001. The TSA, which federalized airport security, was established in November 2001. After 9/11, only ticketed flyers were allowed past security, and cockpit doors were bulletproofed. Flying has completely changed since Al Qaeda hijackers carried out the terrorist attacks of September 11, 2001, 25 years ago. The newly created Transportation Security Administration replaced the private screening checkpoints that flyers were used to and introduced a new normal at airports — one where water bottles are emptied, bodies are scanned, and goodbyes are said before reaching the gate. The planes were similarly hardened with bulletproof doors and the strictest protocols for cockpit access; pilots and flight attendants also received additional training to handle terrorists. Arik Arad, who advised the President's Commission on Aviation Security and Terrorism following the 1988 bombing of Pan Am Flight 103 and served as head of security at Israel's Ben Gurion Airport, said that these changes were part of a post-9/11 paradigm shift favoring a layered approach to security. "The principle is simple — if one layer fails, another should detect or stop the threat," Arad, who now operates an aviation cybersecurity company, told Business Insider. "Intelligence, passenger assessment, screening, baggage security, airport access control, aircraft protection, trained personnel, and law enforcement all became parts of an interconnected security system. That change in philosophy was, in my view, more important than any individual technology introduced after the attacks." Here are the biggest ways flying has changed since 9/11. After the September 11 attacks, airport security was federalized through the establishment of the Transportation Security Administration. CHICAGO - SEPTEMBER 10: A security worker with the Transportation Security Administration (TSA) screens a travelers belongings September 10, 2002 in Terminal 1 at O'Hare International Airport in Chicago, Illinois. Over 500 new federally trained security workers took over the screening work today at security checkpoints in the airport's largest terminal, replacing workers from Argenbright Security. Tim Boyle/Getty Images Before 9/11, airport security was handled by numerous private companies. In November 2001, the Aviation and Transportation Security Act established the Transportation Security Administration, a federal agency whose trained workers took over security screening at airport checkpoints by November 2002. There are still 20 US airports that use private contractors instead of federal employees through the TSA's Screening Partnership Program. In an effort to curb staffing shortages and long security lines resulting from missed paychecks during government shutdowns, the Trump administration is pushing for greater privatization. The agency has also come under scrutiny for its effectiveness. In 2015, an internal Department of Homeland Security investigation found that the TSA failed to detect weapons and fake explosives carried by undercover agents 95% of the time, leading the acting head of the Transportation Security Administration to be reassigned. Cockpit doors were reinforced. 396032 01: Chief pilot of JetBlue Airways Lanny McAndrew, stands behind one of the new bullet-force-resistant cockpit doors that have been installed on all JetBlue planes after the September 11 attacks, October 17, 2001 at JFK airport in the New York borough of Queens. The reinforced cockpit doors, which cost the company approximately $10,000 per aircraft, are the first such doors to be installed on a major carrier. Spencer Platt/Getty Images Flight attendants used to have keys to open the cockpit from the outside. After 9/11, the cockpit got reinforced, bullet-resistant doors and could only be opened from the inside once locked. More air marshals were placed on flights. A federal air marshal service instructor at the TSA training center in Atlantic City, New Jersey. Rachel Wisniewski/The Washington Post via Getty Images In the years following the September 11 terrorist attacks, thousands of new air marshals were added to the Federal Air Marshal Service, which previously had fewer than 50, according to the Government Accountability Office. Pilots and flight attendants received more training in defensive tactics. ARTESIA, N.M. - OCTOBER 16: Unidentified commercial airline pilots practice defensive tactics in a Boeing 727 at the Federal Law Enforcement Training Center October 16, 2003 in Artesia, New Mexico. U.S. commmercial airline pilots take this course and others during the 56 hour, six-day Federal Flight Deck Officer training program, implemented by the TSA. Pilots are instructed in the use of firearms and other defensive tactics on board airplanes. Successful completion of the voluntary course is required before a pilot is permitted to carry a firearm onboard a commercial airplane. Jake Schoellkopf/Getty Images Mark Stephens, a retired Delta Air Lines pilot who flew for the airline for 30 years, told Business Insider that pilots were previously trained to accommodate hijackers' demands and take them where they wanted to go in order to buy time. That changed once the 9/11 terrorist attacks showed how planes themselves could be used as a weapon. "Up until September 11th, using the airplane as a kamikaze-type thing was never, ever, ever discussed," he said. After 9/11, pilots received additional defensive training focused on thwarting potential cockpit invasions and fending off attackers while seated at the controls. The Federal Flight Deck Officer program, launched in 2003, also authorized qualified pilots to carry firearms on board. More bomb-sniffing dogs were deployed to airports. WASHINGTON - DECEMBER 23: Ben (L), a member of the Transportation Security Administration Explosives Detection Canine Team, sniffs luggage under handler Corporal Deborah Myers' (L) guidance during a news conference introducing the team at Ronald Reagan National Airport December 23, 2002 in Washington, DC. Airports across the nation are coming up on the Transportation Security Administration's December 31 deadline of screening all checked luggage. Alex Wong/Getty Images Bomb-sniffing dogs had been used for security sweeps before 9/11, but the TSA took over and expanded the program in 2002, training dogs to detect explosives in and around the airport, including on persons and luggage. In 2025, the TSA's Canine Training Center deployed 1,076 transportation security specialist canine teams and traditional explosives detection canine teams at more than 100 US airports. By the end of 2002, all checked bags were screened for explosives. LOS ANGELES CA-090711- An airline bag handler helps a TSA officer as she puts luggage through X Ray machines at LAX. Airports throughout the country have increased security in the wake of the upcoming 10 year anniversary of the September 11 attacks in New York. J. Emilio Flores/Corbis via Getty Images The Aviation and Transportation Security Act mandated the screening of all checked bags for explosives, weapons, and other dangerous items — a requirement that had not previously been required or widely practiced. The TSA said it's mainly looking for weapons and explosives. TSA employees working with an explosives detection system. Alex Wong/Getty Images The TSA's website said its systems are designed to "detect potential threats to aviation and passengers," and its "security officers do not search for illegal drugs" but will refer any found to law enforcement. Only ticketed passengers were allowed past security. A passenger approaches a security check point at Logan International Airport in Boston on Thursday, Sept. 20, 2001. There has been heightened security at all airports following the terrorist attack on the World Trade Center towers. Officials, lawmakers and safety experts say airport security should be drastically improved and perhaps billions of dollars should be invested in high-tech surveillance and other anti-terrorist tools. Michael DWYER/Gamma-Rapho via Getty Images People who were not traveling themselves used to be able to go through airport security to drop off or meet ticketed passengers at the gate. After 9/11, with few exceptions, only ticketed passengers were allowed past security checkpoints. This security standard is beginning to change. In September, the TSA launched a Gateside pass program allowing TSA PreCheck members and those with a Known Traveler Number from other trusted travel programs who register in advance to go through security without a boarding pass at 13 US airports. Orlando International Airport has a similar program in coordination with the TSA. In 2006, carry-on liquids were restricted to 3.4 ounces as a result of a foiled terrorist plot involving liquid explosives. A Transportation Security Administration (TSA) agent monitors travelers at the TSA security checkpoint at Dallas Love Field Airport (DAL) in Dallas, Texas, US, on Thursday, Aug. 28, 2025. For the first time in almost 20 years, pre-flight screening as of last month no longer requires passengers to take off their shoes and run them through X-ray machines, and officials have signaled they intend to ease the rule limiting containers of carry-on liquids to no more than 3.4 ounces. Shelby Tauber/Bloomberg via Getty Images In 2006, UK authorities uncovered a planned terrorist attack involving liquid explosives hidden in bottles of soft drinks that would have been detonated on planes traveling to the US and Canada. As a result, the US temporarily banned all liquids and gels in carry-on luggage, with exceptions for items like baby formula, breast milk, and prescription medications. The restriction was then adjusted to any liquids and gels larger than 3.4 ounces, a rule that remains in place at TSA checkpoints. Full-body scans were added to TSA screenings after an attempted bombing in 2009. ARLINGTON, VA - DECEMBER 30: Transportation Security Administration Security Officer Nyamsi Tchapleu looks at images created by a "backscatter" scanner during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. Backscatter technology uses low level x-rays to create a two-sided image. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. The TSA will roll out 150 backscatter scanners in 2010 and has budgeted for 300 additional imaging units. Chip Somodevilla/Getty Images After an Al Qaeda terrorist attempted to detonate explosives hidden in his underwear on a Northwest Airlines flight on Christmas Day in 2009, the TSA implemented full-body scans, known as advanced imaging technology, into screening. The machines use millimeter wave technology to detect both metallic and non-metallic items. TSA Precheck was introduced in 2011 to expedite security lines for vetted travelers. NEW YORK, NEW YORK - MARCH 22: People pass through a TSA Pre-check security checkpoint at John F. Kennedy International Airport on March 22, 2026 in New York, New York. The travel disruptions continue as hundreds of TSA agents quit or work without pay during a partial government shutdown. U.S. President Donald Trump said ICE agents will be deployed to U.S. airports on Monday, with border czar Tom Homan in charge of the effort. (Photo by Adam Gray/Getty Images) Adam Gray/Getty Images Travelers who apply for TSA PreCheck undergo a background check and, if approved, pay up to $85 to receive a Known Traveler Number. TSA PreCheck allows passengers to wait in separate, faster-moving security lines with fewer restrictions. Post-9/11, Arad said intelligence agencies worldwide worked more closely together on aviation security. UNITED STATES - SEPTEMBER 18: The seal of the Central Intelligence Agency is displayed in the foyer of the original headquarters building in Langley, Virginia, U.S., on Friday, Sept. 18, 2009. CIA Director Leon Panetta said this week he never contemplated resigning over a newly begun Justice Department inquiry into tactics used during interrogations of terrorist suspects. Andrew Harrer/Bloomberg via Getty Images Beyond the airport gates, Arad told Business Insider that intelligence agencies across countries started sharing information more openly to flag potential threats, a change he witnessed firsthand as head of security at Ben Gurion Airport. "We share information, and it helps, because if there is a bad guy in Germany and he's planning on coming to the US, people are aware of it and they're waiting for him," Arad said. "I'm telling you, I know it. I've been there." Read the original article on Business Insider

A TSA security checkpoint at John Wayne Airport in Santa Ana, California.Jeff Gritchen/MediaNews Group/Orange County Register via Getty Images Aviation security was completely overhauled after the terrorist attacks of September 11, 2001. The TSA, which federalized airport security, was established in November 2001. After 9/11, only ticketed flyers were allowed past security, and cockpit doors were bulletproofed. Flying has completely changed since Al Qaeda hijackers carried out the terrorist attacks of September 11, 2001, 25 years ago. The newly created Transportation Security Administration replaced the private screening checkpoints that flyers were used to and introduced a new normal at airports — one where water bottles are emptied, bodies are scanned, and goodbyes are said before reaching the gate. The planes were similarly hardened with bulletproof doors and the strictest protocols for cockpit access; pilots and flight attendants also received additional training to handle terrorists. Arik Arad, who advised the President's Commission on Aviation Security and Terrorism following the 1988 bombing of Pan Am Flight 103 and served as head of security at Israel's Ben Gurion Airport, said that these changes were part of a post-9/11 paradigm shift favoring a layered approach to security. "The principle is simple — if one layer fails, another should detect or stop the threat," Arad, who now operates an aviation cybersecurity company, told Business Insider. "Intelligence, passenger assessment, screening, baggage security, airport access control, aircraft protection, trained personnel, and law enforcement all became parts of an interconnected security system. That change in philosophy was, in my view, more important than any individual technology introduced after the attacks." Here are the biggest ways flying has changed since 9/11. After the September 11 attacks, airport security was federalized through the establishment of the Transportation Security Administration. CHICAGO - SEPTEMBER 10: A security worker with the Transportation Security Administration (TSA) screens a travelers belongings September 10, 2002 in Terminal 1 at O'Hare International Airport in Chicago, Illinois. Over 500 new federally trained security workers took over the screening work today at security checkpoints in the airport's largest terminal, replacing workers from Argenbright Security.Tim Boyle/Getty Images Before 9/11, airport security was handled by numerous private companies. In November 2001, the Aviation and Transportation Security Act established the Transportation Security Administration, a federal agency whose trained workers took over security screening at airport checkpoints by November 2002. There are still 20 US airports that use private contractors instead of federal employees through the TSA's Screening Partnership Program. In an effort to curb staffing shortages and long security lines resulting from missed paychecks during government shutdowns, the Trump administration is pushing for greater privatization. The agency has also come under scrutiny for its effectiveness. In 2015, an internal Department of Homeland Security investigation found that the TSA failed to detect weapons and fake explosives carried by undercover agents 95% of the time, leading the acting head of the Transportation Security Administration to be reassigned. Cockpit doors were reinforced. 396032 01: Chief pilot of JetBlue Airways Lanny McAndrew, stands behind one of the new bullet-force-resistant cockpit doors that have been installed on all JetBlue planes after the September 11 attacks, October 17, 2001 at JFK airport in the New York borough of Queens. The reinforced cockpit doors, which cost the company approximately $10,000 per aircraft, are the first such doors to be installed on a major carrier.Spencer Platt/Getty Images Flight attendants used to have keys to open the cockpit from the outside. After 9/11, the cockpit got reinforced, bullet-resistant doors and could only be opened from the inside once locked. More air marshals were placed on flights. A federal air marshal service instructor at the TSA training center in Atlantic City, New Jersey.Rachel Wisniewski/The Washington Post via Getty Images In the years following the September 11 terrorist attacks, thousands of new air marshals were added to the Federal Air Marshal Service, which previously had fewer than 50, according to the Government Accountability Office. Pilots and flight attendants received more training in defensive tactics. ARTESIA, N.M. - OCTOBER 16: Unidentified commercial airline pilots practice defensive tactics in a Boeing 727 at the Federal Law Enforcement Training Center October 16, 2003 in Artesia, New Mexico. U.S. commmercial airline pilots take this course and others during the 56 hour, six-day Federal Flight Deck Officer training program, implemented by the TSA. Pilots are instructed in the use of firearms and other defensive tactics on board airplanes. Successful completion of the voluntary course is required before a pilot is permitted to carry a firearm onboard a commercial airplane.Jake Schoellkopf/Getty Images Mark Stephens, a retired Delta Air Lines pilot who flew for the airline for 30 years, told Business Insider that pilots were previously trained to accommodate hijackers' demands and take them where they wanted to go in order to buy time. That changed once the 9/11 terrorist attacks showed how planes themselves could be used as a weapon. "Up until September 11th, using the airplane as a kamikaze-type thing was never, ever, ever discussed," he said. After 9/11, pilots received additional defensive training focused on thwarting potential cockpit invasions and fending off attackers while seated at the controls. The Federal Flight Deck Officer program, launched in 2003, also authorized qualified pilots to carry firearms on board. More bomb-sniffing dogs were deployed to airports. WASHINGTON - DECEMBER 23: Ben (L), a member of the Transportation Security Administration Explosives Detection Canine Team, sniffs luggage under handler Corporal Deborah Myers' (L) guidance during a news conference introducing the team at Ronald Reagan National Airport December 23, 2002 in Washington, DC. Airports across the nation are coming up on the Transportation Security Administration's December 31 deadline of screening all checked luggage.Alex Wong/Getty Images Bomb-sniffing dogs had been used for security sweeps before 9/11, but the TSA took over and expanded the program in 2002, training dogs to detect explosives in and around the airport, including on persons and luggage. In 2025, the TSA's Canine Training Center deployed 1,076 transportation security specialist canine teams and traditional explosives detection canine teams at more than 100 US airports. By the end of 2002, all checked bags were screened for explosives. LOS ANGELES CA-090711- An airline bag handler helps a TSA officer as she puts luggage through X Ray machines at LAX. Airports throughout the country have increased security in the wake of the upcoming 10 year anniversary of the September 11 attacks in New York.J. Emilio Flores/Corbis via Getty Images The Aviation and Transportation Security Act mandated the screening of all checked bags for explosives, weapons, and other dangerous items — a requirement that had not previously been required or widely practiced. The TSA said it's mainly looking for weapons and explosives. TSA employees working with an explosives detection system.Alex Wong/Getty Images The TSA's website said its systems are designed to "detect potential threats to aviation and passengers," and its "security officers do not search for illegal drugs" but will refer any found to law enforcement. Only ticketed passengers were allowed past security. A passenger approaches a security check point at Logan International Airport in Boston on Thursday, Sept. 20, 2001. There has been heightened security at all airports following the terrorist attack on the World Trade Center towers. Officials, lawmakers and safety experts say airport security should be drastically improved and perhaps billions of dollars should be invested in high-tech surveillance and other anti-terrorist tools.Michael DWYER/Gamma-Rapho via Getty Images People who were not traveling themselves used to be able to go through airport security to drop off or meet ticketed passengers at the gate. After 9/11, with few exceptions, only ticketed passengers were allowed past security checkpoints. This security standard is beginning to change. In September, the TSA launched a Gateside pass program allowing TSA PreCheck members and those with a Known Traveler Number from other trusted travel programs who register in advance to go through security without a boarding pass at 13 US airports. Orlando International Airport has a similar program in coordination with the TSA. In 2006, carry-on liquids were restricted to 3.4 ounces as a result of a foiled terrorist plot involving liquid explosives. A Transportation Security Administration (TSA) agent monitors travelers at the TSA security checkpoint at Dallas Love Field Airport (DAL) in Dallas, Texas, US, on Thursday, Aug. 28, 2025. For the first time in almost 20 years, pre-flight screening as of last month no longer requires passengers to take off their shoes and run them through X-ray machines, and officials have signaled they intend to ease the rule limiting containers of carry-on liquids to no more than 3.4 ounces.Shelby Tauber/Bloomberg via Getty Images In 2006, UK authorities uncovered a planned terrorist attack involving liquid explosives hidden in bottles of soft drinks that would have been detonated on planes traveling to the US and Canada. As a result, the US temporarily banned all liquids and gels in carry-on luggage, with exceptions for items like baby formula, breast milk, and prescription medications. The restriction was then adjusted to any liquids and gels larger than 3.4 ounces, a rule that remains in place at TSA checkpoints. Full-body scans were added to TSA screenings after an attempted bombing in 2009. ARLINGTON, VA - DECEMBER 30: Transportation Security Administration Security Officer Nyamsi Tchapleu looks at images created by a "backscatter" scanner during a demonstration at the Transportation Security Administration's Systems Integration Facility at Ronald Reagan National Airport December 30, 2009 in Arlington, Virginia. Backscatter technology uses low level x-rays to create a two-sided image. The scan can detect hidden metallic and nonmetallic objects such as weapons and explosives without physical contact. The TSA will roll out 150 backscatter scanners in 2010 and has budgeted for 300 additional imaging units.Chip Somodevilla/Getty Images After an Al Qaeda terrorist attempted to detonate explosives hidden in his underwear on a Northwest Airlines flight on Christmas Day in 2009, the TSA implemented full-body scans, known as advanced imaging technology, into screening. The machines use millimeter wave technology to detect both metallic and non-metallic items. TSA Precheck was introduced in 2011 to expedite security lines for vetted travelers. NEW YORK, NEW YORK - MARCH 22: People pass through a TSA Pre-check security checkpoint at John F. Kennedy International Airport on March 22, 2026 in New York, New York. The travel disruptions continue as hundreds of TSA agents quit or work without pay during a partial government shutdown. U.S. President Donald Trump said ICE agents will be deployed to U.S. airports on Monday, with border czar Tom Homan in charge of the effort. (Photo by Adam Gray/Getty Images)Adam Gray/Getty Images Travelers who apply for TSA PreCheck undergo a background check and, if approved, pay up to $85 to receive a Known Traveler Number. TSA PreCheck allows passengers to wait in separate, faster-moving security lines with fewer restrictions. Post-9/11, Arad said intelligence agencies worldwide worked more closely together on aviation security. UNITED STATES - SEPTEMBER 18: The seal of the Central Intelligence Agency is displayed in the foyer of the original headquarters building in Langley, Virginia, U.S., on Friday, Sept. 18, 2009. CIA Director Leon Panetta said this week he never contemplated resigning over a newly begun Justice Department inquiry into tactics used during interrogations of terrorist suspects.Andrew Harrer/Bloomberg via Getty Images Beyond the airport gates, Arad told Business Insider that intelligence agencies across countries started sharing information more openly to flag potential threats, a change he witnessed firsthand as head of security at Ben Gurion Airport. "We share information, and it helps, because if there is a bad guy in Germany and he's planning on coming to the US, people are aware of it and they're waiting for him," Arad said. "I'm telling you, I know it. I've been there." Read the original article on Business Insider