This is really heartbreaking because I had once a flight with sriwijaya back in 2011, the age of the plane is indeed an old. I do not know how good the maintenance of the company is but what I know is that the pilot is experienced even when the weather is bad and almost uncontrollable if I'm not mistaken in 2016 he can landing the plane safely
airline companies often falsify documents in order to avoid maintenance costs. I don't remember well, I believe it was an accident involving italian airlines, either way eurpean, like 15 or 20 years ago, they saved on the liquid that is de-icing the airplane before starting (they use a substance like a spray over the airplane), in the end the airplane crashed due to icing.
the airplane wasn't old.
But to allow an airplane that old to still be active...don't know. if the airplane checks all securities...on the other hand we see what happened with the new boeing max and everything that they've lied about hiding the dangers and not even informing the pilots about the nose and balance issue, as well as the automatically correction which led to both crashes