Clench and Grunt - Blue Angels Aerobatics team

[Lance B]

That "smile" is part of a "clench & grunt" -- a technique to stave off blackout during high positive G manoeuvres. The pilots wear a "G suit" which inflates around their lower body during high G to keep blood in the upper body. The "clench & grunt" is a tensing of muscles to keep blood in the head from draining out and depriving the brain of the oxygen it needs for the pilot to remain conscious. It's explained a bit at http://www.businessinsider.com/how-pilots-survive-inhuman-levels-of-g-force-2014-11, where it's termed "AGSM". Also see https://en.wikipedia.org/wiki/High-G_training.

A different view of the Blue Angels

Just watch the pilot's teeth and jaw and he seems to "bear down" as he goes into turns etc, quite amusing. Interestingly, I have a photo of me on a particularly vigorous roller coaster ride doing a similar thing! It looks like I'm trying to pass a brick!

Also, in some shots you see his nose indent in as the G forces cause it to dimple.

https://www.youtube.com/embed/u4D0yx4DvBk?rel=0

[Glenda]

Looks like he's in pain. Watching him constantly turn his head looking all around I wondered how much they actually see travelling at that speed, and how fast their reaction has to be to correct if they get too close to one another.