Mainly conflict zones. Currently in Middle East. In my experience, you can get almost anything through most airports if it's in your hold luggage. Obviously don't take a knife in your hand carry.
You can have a Swiss Army multi tool in yours pockets on the streets of Istanbul or Lebanon !.
Every airline & airports have a list of prohibited items , it's 2021 not 1999 !. Inform yourself !.
You can buy drinking water @ the airport , but you will NOT take 1/2 L of liquid on the flight !.
Detectors & 360 degrees body scanning is on all airports !.
Try to bring a Spyderco on airports like Singapore, Tokyo, Sydney,...........
Again, it's 2021