Doesn't help that most people were also pre-conditioned for the event over 30 years in advance.

Here are a few examples...

1963
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1973
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1974
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1975
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1976
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1979
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1983
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1985
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1987
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1988
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1990
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1991
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1993
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1994
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1996
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1997
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1998
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1999
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2001
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Oh and you can't forget the Lone Gunmen pilot episode which aired on FOX in March 2001 with the plot of a shadow group within the US government taking control of a commercial airliner (via remote) with the intention of crashing it into the WTC. And it just so happens that this episodes plot was pitched to one of the main actors of the show (Dean Haglund) by 3 CIA agents that were fans of his previous work (X-Files). Dean then pitched the idea to the show creator Chris Carter which decided to create a new show around it (which became The Lone Gunmen). This pilot episode also includes the murder of a man that was getting to close to the truth by using a controlled car crash made to look like an accident (***cough*** Michael Hastings ***cough***).