Good point about the gut feeling of pilots possibly being groomed for proving flights. I thought it was a good indication firestream said the crew is still at Willow Run. If training is done and nothing else was planned, all would have left by now IMO.

Never thought about the fact that probably not a whole lot of pilots would have proving flight experience. IMO, they would need to be briefed on what to expect in proving flights, as well as to go through all the manuals to know the details so they are ready for anything that might be thrown at them.