I dunno if I can think of a "favourite" conspiracy theory, but I did come up with what I think is a much better version of the "remote controlled planes were used in 911" theory.
Remember the
Marconi scientists die mysteriously stuff from many years ago? Well, most of those guys were working on various kinds of remote telemetry. Precisely the sort of thing you'd need if you were going to turn a large Boeing into a remote controlled cruise missile.
Let's pretend that some ultra-dodgy spooks connected to the people who later show up in the PNAC crew got hold of what they'd been working on under Star Wars contracts and bumped them off to make sure there were no tale bearers later. Maybe someone from the World Anti-Communist League, or Michael Ledeen's "strategy of tension" Italian neo-fascist pals, they know how to keep a secret. I'd see Ledeen as the obvious cut out for this stuff, 'cos he's connected to all of the PNAC gang, but he's also connected to serious neo-fascist terrorists and the P2 lodge (according to various Italian court cases that investigated all this stuff), he's tight with the most extreme Israelis and he's a big fan of Machiavelli and Mussolini. So if I were writing a conspiracy novel, he'd be a key character.
Next problem, having the technology is how to get it onto all of the planes. Nothing could be simpler. To do that, they'd just need to covertly fiddle with the (Israeli produced) software used to control maintainance on such planes, and get their kit installed during routine upgrades without arousing suspicion.
I think this is pretty unlikely, but I also think it makes a more satisfying narrative than anything the professional CT'ers have come up with so far.
What's worrying though, is that some other scientists got mysteriously killed if you recall, and the second wave of
mystery scientist deaths were all germ warfare specialists or worked in closely related fields. So one seriously wonders what *they* have in mind next.