It Was Shoes On, No Boarding Pass Or ID. But Airport Security Forever Changed On 9/11

https://www.npr.org/2021/09/10/ [login to see] /911-travel-timeline-tsa
It's hard to fathom now, but we used to be able to arrive at the airport just minutes before a flight. We'd keep our shoes and coats on as we went through a simple metal detector, and virtually anyone could go right to the gate without a boarding pass or even showing an ID.

The 19 al-Qaida-affiliated terrorists who hijacked four commercial jetliners on Sept. 11, 2001, knew that and exploited lax airport security measures, strolling through metal detectors at four airport security checkpoints with ease, with deadly weapons in hand. It allowed the hijackers to commandeer those airplanes and use them as jet fuel-filled missiles as they flew them into the twin towers of the World Trade Center, the Pentagon and a field in Shanksville, Pa., killing nearly 3,000 people.

"It was so easy, a lot of us were surprised it hadn't happened sooner," says Jeff Price, who was assistant security director at Denver International Airport on Sept. 11, 2001, and is now an aviation security expert at Metropolitan State University in Denver.

Airport security at that time was done by private contractors, usually hired by the airlines, with few federal standards. Those security contracts usually went to the lowest bidder.