Despite that orange bit in front of my name, and that I've found answers to questions more abstruse than this, I remain surprised to find that some questions have been asked before! More can always be said on any topic at all, of course, so if anyone would like to comment on the 1970s hijackings and contrast them to the post-9/11 environment (oh god we can say that now on the sub), please don't let this post stop you! More posts are always welcome.

For the meantime, OP, we can look to some older posts that also ask the same question you did of the 1970s hijackings. u/cryptovariable covers the security response to the 1970s hijackings; while u/cdesmoulins looks at the causes and motives behind the 1970s hijackings.

Another link in next post because argh tag limit.