While the loss of life of ~3k people, once, is regrettable, it is by no means an event worth the response that has occurred. Sometimes, you are just unlucky, and we aren't going to reconfigure entire systems at enormous cost when it is unlikely the event will happen again. It is very hard for people to internalize this. "Do something!" and what not. Armoring flight deck doors would've been sufficient to prevent a recurrence. Instead, the TSA spends ~$8B/year and employs ~60k federal workers. For 3k people who died once.
Conversely, there are ~40k-50k gun deaths annually in the US, and we do nothing, despite that being a much greater risk than an air transport terror attack.
https://www.pewresearch.org/short-reads/2023/04/26/what-the-...