This is down to your parents really. $60,000 flat over 15 years is a repayment schedule of $334 per month. If your parents feel they can comfortably afford this loan and are prepared to help you in this way then fine. In reality they would have to take the viewpoint that the money is a write off.
The reality of obtaining a return on completion of the training is in all probability remote. The likelyhood of enormous cost overruns is very high and even then there are simply no guarantees.
I am sure your parents (like most parents) are always trying to do the best for their children, but they are rarely suicidal when it comes to the families assets no matter what dreams their progeny may be chasing.
The way to look at this is to substitute the "flying training" bit for a "automobile" or "vacation". Sometimes those things can be dreams to, but as expenditure they are more common and better understood. If you cant afford to potentially write the cost off, then do not borrow money you cannot cover to purchase it.