I mean for God's sake they were in existence before 9/11 what more do you need?
They flew to the moon in 1969. Are you saying a 757 could fly to the moon? I hope not, because a 757 is neither designed nor equipped to fly to the moon, and if someone manipulated it thusly, someone would notice even before take-off.
What a dumb line of reasoning!
Yeah, maybe. But it can't involve remote control.
Because everyone except you understands that remote control of a plane is only possible if it is designed and equipped for that purpose.
Let's do another car analogy: In 2008,
ESC was well introduced to automobiles. It "is a computerized technology that improves safety of a vehicle's stability by detecting and minimizing skids". In August of that year, I drove my Toyota Corolla a little carelessly on wet mouintain road, lost control and skidded into the ditch.
How was that possible - should ESC not have prevented this from happening?
NO! Why?
Because my Toyota Corally was not equipped with ESC! Get it? It is not a matter of changing computer software - you have to install things in my Corolla!
Or, an even closer analogy: Remote controlled vehicles have been around for a long time. Now, could a software change to my Corolla make it a remote-controlled car? No way! It has no device to turn the steering wheel (or turn the front wheels wothout applying the steering wheel).
Suppose someone would manipulate my Corolla to make it remote controlled - would I notice? Possibly. Would the guys at the garage notice? Hell yes!
Four planes owned and maintained by American Airlines and United Airlines? Really? Without them noticing, or with their approval?
So add AA and UA to your growing list of conspirators, right?