You can actually kind of see both the bronze age collapse (around 1000 BCE) and the early medieval dark ages (around 400 to 800 AD)

Maybe it's just an impression, but didn't air travel become much more affordable over the last 20 years? I remember when I was a kid, going to Japan or Thailand was a whole endeavour, you saved for it for years, it was the adventure of a lifetime, now it feels like any reasonably affluent middle-class couple can afford it without much fuss...