If your goal, as a terrorist organization, was to economically wound an industry while killing as many individuals as possible... you really couldn't ask for a better target than dozens (if not hundreds) of people standing around waiting to get through airport security.
Clearly, the solution is to have some pre-security security checks. /s
Sadly, you're suggestion will be mentioned if this happens I'm sure. But instead of a physical step before the gates, it will be a mental one. What place could you check people prior to them being physically checked before boarding?
When they think about using an airplane. When someone thinks about travelling, the TSA will locate and travel to them, and direct the citizen through their thought crime machine. If you refuse, then the TSA strip search you and inspect your orifices in public, which will also be the next step from private rooms. /s
Security is a feeling. Also, there are events and odds. The events and odds don't make me feel like policy is needed for me to feel safe travelling IMO. What happens happens. If someone tries to logically attempt to cast blame upon a party for something like a bombing for not preemptively stopping it, then I'll just point to the math surrounding the TSA. IT MAKES NO SENSE.
If your goal, as a terrorist organization, was to economically wound an industry while killing as many individuals as possible... you really couldn't ask for a better target than dozens (if not hundreds) of people standing around waiting to get through airport security.
Clearly, the solution is to have some pre-security security checks. /s