It would seem that surviving a plane crash and surviving 40 days in a jungle without adults, are two distinct classes of "miracle".

There is little you can really do to ensure that you survive a plane crash. Perhaps not much more than assuming a safe bodily posture. It's really going to be up to fate, and depend on the type of crash, and possibly also on the crew's ability to mitigate the worst of it.

Surviving in the jungle means that you were able to secure food, water, shelter, and avoid deadly situations. Indigeneous jungle-dwellers are arguably way more equipped to do that, but still, lacking adults or adequate supplies, quite a feat, I'd say.

To make it through both ordeals alive is definitely a cumulative miracle, and bravo to the kids for their bravery and persistence.