Haha, oddly enough there was a period where there were almost daily hijackings of aircraft! The most common period for plane hijackings was 1961-1972. It was just a thing that happened sometimes and people totally just rolled with it. Sometimes your plane was hijacked and you landed in Cuba. Whatev, if happens: https://www.vox.com/2016/3/29/11326472/hijacking-airplanes-e...

That's why we added the metal detectors. Reinforcing the cockpit doors may have been an okay response to the events of 9/11 and potentially would have been sufficient to prevent most major terrorist attacks that seek to use the plane itself as a weapon rather than merely destroying it. (Also people will generally gang up to attack hijackers now rather than just remaining calm and letting them fly the plane elsewhere. Which sufficiently changes the dynamic.)