Here's an interesting irony

[Drew Phipps]

It turns out that Joseph Kennedy, older brother of JFK, died during a mission code-named "Operation Aphrodite" which is described as follows by wiki:

"Operation Aphrodite (US Army Air Forces) & Operation Anvil (US Navy) made use of unmanned, explosive-laden Army Air Forces Boeing B-17 Flying Fortress and Navy PB4Y-1 Liberator bombers, that were deliberately crashed into their targets under radio control.[SUP][/SUP]"

(Apparently the target sight of the elder Kennedy's operation was a V-2 launch site.)

So, not only is the idea that "planes can be deliberately flown into buildings as bombs" not surprising in 2001, it had actually formed part of the US Armed Forces strategic planning ~60 years before. (And, apparently there was some rudimentary form of remote control.)

[David Guyatt]

Probably got the idea from the Japanese Kamikaze pilots targeting US carriers and other warships...

[Michael Barwell]

The 1918 Kettering Bug was an experimental, unmanned aerial torpedo, a forerunner of present-day [size=12]cruise missiles[/SIZE]. It was capable of striking ground targets up to 121 kilometres (75 mi) from its launch point, while traveling at speeds of 80 kilometres per hour (50 mph).[size=12][1][/SIZE]
https://en.wikipedia.org/wiki/Kettering_Bug