https://en.wikipedia.org/wiki/List_of_aircraft_hijackings
Plane hijacking has been on its way out anyway after the turmoil of the 1970s. And that has probably more to do with a) the relative political stability of the post cold war period, and b) a general sense that airplane hijacking isn’t actually that likely to advance your political goals. If you read the list above, you see people hijacking planes all kinds of dumb methods, hardly any of them involves carrying an actual bomb onto the plane.
Back in the day you needed to get onto TV and into newspaper headlines to get any attentions besides your neighbours. Today you can do that with a Facebook page and send your ideas worldwide.
And that works the back way too: instead of the news of bombing in some remote country you can't even find on the map you can get a funny cat videos to fill in.
Today the cops are doing the job of the right wing counter-revolutionary groups, and relatively rarely do we get the right wing counter revolutionary terror attacks (but we definitely still do; just not as much). Meanwhile the left has pretty much abandoned terrorism as a viable tactic. It is mostly employed as part of an anti-colonial struggle of an oppressed minority sometimes under literal occupation of their colonizer’s military. But alas we only have a fraction of colonies today relative to the 1970s and the 1980s.
Most plane hijackings/bombings were middle east related (e.g. linked to one of Palestinian liberation, al-qaeda, or isis)
Not sure i'd call that a stable region of the world, especially now. Perhaps though the people involved just realized it was an ineffective strategy.
I don‘t like it (in fact I hate it), but capitalism won the cold war. And communist revolutionaries went dormant as a result. The cold war brought a different kind of stability, particularly to Europe, and the end of it created a massive turmoil (mainly along nationalistic lines rather then political ideological ones).
In hindsight perhaps I should have been more specific and said “relative political stability along ideological lines.”