I don't want to get into the ever-shifting, ever-adapting arguments in favor of the conspiracy theories, but I'll say this.
4 aircraft took off and never landed. These aircraft were full of real people, all of whom have families, co-workers, friends, acquaintances. All of whom purchased tickets went through airport security and boarded their aircraft. These aircraft were staffed by real pilots, stewards/stewardesses. They were assisted by real luggage handlers, air-traffic controllers, etc. These were normal flights that flew the same route every day. Had there been no such flights that day someone would have noticed, someone would have asked why.
There would literally have to be several thousand people who know something didn't happen that should have happened, and several thousand who would know that something happened that should not have happened. People who couldn't all possibly have an interest in keeping secret the truth.
Those planes took off. One hit WTC 1, one hit WTC 2, one hit the Pentagon and another crashed into a field. The magnitude of faking those flights is so incredibly enormous as to be completely inconceivable. The only way to believe those flights were not real is to create a fantasy in which they are not real and then convince yourself that fantasy is reality. That's exactly what way too many people have done.
It is absolutely ****ing sad. I'm so done with the madness of it.