What to do for Father (89) aspirating while eating? Anyone have this experience?

The best answer to this question is from the speech therapist. If it's solely from acid reflux, then that would have to be addressed. Whether or not your father can eat solid foods again really is something a medical person would need to answer.

I've been told by either a nurse or speech therapist (don't remember which) that swallowing functions can deteriorate with age. That might be a factor too.

You might also want to ask the speech therapist about exercises, such as the Shaker exercises, and ask if your father is a candidate. They seem simple but can be uncomfortable, but they work well when done properly.

So go to the speech twrapist who can assess his swallowing. With therapy, this can improve.