I have to agree with everyone on the NYX sunglasses. The amber seem to work best for most flying and the Vermillion work great with heavy overcast or evening light... for me. The dark grey seem to be good only for the brightest of conditions. The only downfall to these is the lens can crack right at the middle where the notch is that holds them in place on the frames. You have to be carefull when taking the lens off the frames. Mine started to get a hairline crack there and I fixed them by putting a small square of light c.f. ca'd to the back side of the lens. You can get different color lens through NYX website for all kinds of applications.
You can also get prescrition inserts that set on the inside of the lens.

Wayne G.