Whilst I would agree with all of you Grett Optic fans that their product is very good (I have several of their sun readers) I have to say that I no longer wear them when flying.
The reason is that I have come to rely very much on my Airspace Aware unit - and the screen is just not bright enough to read with sunspecs.
Genghis is quite right about the baseball cap option. Works a treat! And less easy to lose too!
Andy