[sandworm101]

>> When inspection frequency gets too high, airlines and authorities decide to save money, leading to less frequent inspections.

More often such aircraft are just retired. One defining difference between upstart airlines and "legacy" airlines is that the upstarts generally have new aircraft with lower inspection requirements. An interesting paper would address the inevitable evolution of new airlines as as their airframes age. When do they first try to transition to higher-profit services? When do they hit their first period of labor unrest? I theorize it is a function of aircraft age.

At least a few airlines don't ever buy aircraft. Instead they lease them with the intention of returning them moment they require more frequent inspections.

[nradov]

Upstart airlines frequently lease used aircraft because they're cheaper.

[rbanffy]

This whole business is so capital-intensive the decisions often follow non-obvious patterns. There are advantages in keeping a fleet uniform, even if a newer plane lease is cheaper than another model you already have a bunch of just because of the costs of training ground and air crews. Some leases may end up cheaper for you - and only for you - because of some tax break you got from one government that, for now, wasn't questioned by the WTO (and, since it's the manufacturer who'll pay the fines, it's not a concern).

It's... complicated. Very complicated.