But, airport security looked very different before Sept. 11, 2001.
Before the attacks, passenger and baggage screenings were generally handled by private companies.
"In some cases, almost like a mom and pop, they had rules provided by the FAA. And the airlines were responsible for having oversight over the security companies," said Jose Flores, deputy director of TSA Illinois.
"You didn't have to take off your shoes. You didn't have to take off your belt. I think they just wanted your laptop. They would just make you turn it on," flyer Jeff Alberin said.
The Sept. 11 attacks exposed major weaknesses in that system.
"We had basic X-rays, walked through metal detectors, handheld metal detectors. But it was cursory, if you will. It wasn't as thorough as we now, in retrospect, would have preferred," Flores said.
Flores was working for American Airlines at the time in St. Louis, Missouri.
He says he was headed to his office when he saw passengers huddled around a TV.
"So I popped my head in the restaurant, and that's when I saw. That's when I saw the World Trade Center. It was incomprehensible to me. The building was on fire, billowing black clouds of smoke. And I just, again, it was incomprehensible. I knew what I was looking at. It just didn't make any sense. And that's when one of my agents came up to me in tears and said, that's American Airlines flight 11," Flores said.
Four commercial airplanes were hijacked that morning. Two crashed into the World Trade Center. One hit the Pentagon. Another went down in Pennsylvania after passengers and crew attempted to take control of the plane.
"We know that on 9/11, the terrorists used fraudulent IDs. We know that they brought box cutters and knives onboard," Flores said.
Nearly 3,000 people were killed.
To help prevent an attack like 9/11 from occurring again, President George W. Bush signed the Aviation and Transportation Security Act into law in November of 2001. The legislation created the Transportation Security Administration.
TSA built a new federal workforce and took over screening operations at airports across the country quickly.
"I will say, it was chaotic. When Congress passed the Aviation and Transportation Security Act, that gave birth to TSA. So the task at hand for the leadership was to build an agency from the ground up. It was a Herculean effort. Hiring, establishing procedures, hierarchies, the ordering supplies., many of the leadership, they were working out of broom closets at airports because we didn't have any space," Flores said.
TSA began operating in 2002. For travelers, airport security became a much bigger part of the flying experience.
Some say it makes them much more comfortable taking to the skies.
"Honestly, I can fly and feel comfortable knowing that extra precautions are being taken," flyer Tiffany Clay said. "I know it can be a hassle getting through, but I'd rather be safe than sorry."
Since 2002 TSA has rolled out biometric screening and expedited security screenings like TSA Precheck and Global Entry. Private companies like Clear offer accelerated entry service for low-threat customers, making the flying experience safer for everyone.
"I think that's why I'm here today with TSA is because I want to make sure, just as my officers want to make sure, that this never happens again. We have a saying, 'not on our watch,'" Flores said.
According to federal officials, there have been no successful large-scale 9/11-style attacks since TSA took over airport screening.