but that's not about the Anthem specifically but it does explain some of the pomp and circumstance surrounding renditions of the Anthem during NFL events. like why they so often have members of the military performing or doing some tricks or whatever during the Anthem. and it explains all of the flyovers w/military jets and stuff like that.
funny story - the whole shit started w/MLB's 1918 World Series. a Navy guy playing for the Cubs saluted the flag when a band played the Anthem in the 7th inning stretch of a Chicago home game where the crowd was pretty dead. the crowd got into it. so when the series rolled into Boston (Cubs-Red Sox in the WS...kill me) the Red Sox had the Anthem in pregame and wrapped it up w/a bunch of injured soldiers and rah-rah (WWI was on). that sealed it. other teams followed suit.
it has infected every pro sports league, so it seems.
but since the military is in bed w/the NFL i'm sure it won't stop there. the military doesn't exactly pay NFL teams to play the Anthem - it seems assumed the teams will play it (contractual requirement at all NFL events) and the military pays for the add-ons. the rah-rah.