At this juncture in time I think it is an UFO. Another event happened a year ago along the same path and they never identified the object.
A couple of threads/articles on the event if anyone is interested in reading them.
http://www.chron.com/disp/story.mpl/front/6455016.html
http://www.freerepublic.com/focus/f-news/2263638/posts
The May 2008 event:
http://www.freerepublic.com/focus/f-news/2021609/posts
But of course!