Apocalypse Right Now?

It's been sounding like the soundtrack of Apocalypse Now here at home for the last half hour, or so.

I went outside and there appears to be a Blackhawk helicopter traveling between the Ann Arbor airport and Michigan Stadium--over and over.

No home football game this Saturday. I wonder what is going on?

UPDATE: Wow. I'm really impressed with Google's indexing. Within ten minutes of posting I thought I'd search to see if I could answer my question. No luck on that, but the top search result was this post.