It's so weird how this case has been active for 27 years, despite the fact that it looks like she was identified literally right after she was found and it's pretty obvious what happened to her. On top of that, her loved ones (at least her parents) were found alongside her, and they appear to have been identified without a doubt, as they are nowhere to be found on any unidentified persons' databases. Kathia/Jane Marathon Doe was inserted into NamUS circa 2016, and NCMEC even gave her a recent facial reconstruction.
I don't know what Cuban refugees would take with them when heading to America, but I'm thinking the reason why the parents were identified right away is that they carried ID or other documents proving their identities. Kathia may have never been "officially" identified because at her age, the likelihood that she'd carry any type of identification would be much less than the odds of her adult parents doing the same. That being said, I really don't know what kinds of documents, if any, they would bring alongside them, given the circumstances.
Also, with the exception of the parents, I have no idea where the other people on the plane ended up or if they've ever been located. Kathia had two younger siblings, if I recall correctly, and there were family friends on the plane as well, and I have no clue when or where they turned up, if ever.