TrashMan,
This is the realm of philosophy of reasoning and many a thesis was written on this - I do not intend to offer one here.
The validity of your experience was never a question. That there are multiple observers and the fact that you are an expert in aviation does add objectivity. All but rules out a halucination
, that sort of thing. Just kidding!
The trouble is that the human eye is not a good observation tool. Mainly, on the account of being attached to the brain which is subjective by it's very nature. What can be said with certainty, is that you all saw something and saw it move. Size, shape, speed, distance too - forget about planet of origin - all can only approximated by eye which is fooled easily enough.
I guess I do not doubt that you saw something remarkable, it is just I doubt that it was piloted by little green men. I would bet on something Earth-created and, ultimately, explainable.