Assuming something is true doesn't make it true. Colluding airport employees as well as rural airports seem like clear vulnerabilities. When thinking about security problems you don't just assume your security measure always succeed and assuming that all passengers are "equal" seems like a poor assumption, especially for an exceptional case by highly motivated people, potentially with state backing.
https://en.wikipedia.org/wiki/Air_West_Flight_612
Here is an example where a man got a gun on a plane in 2007, which directly disproves the 'equality' if passengers.