One time, around late 2009/early 2010 I was laying on the lawn with friends in the middle of the night, we were all viewing the stars and talking.
Suddenly a bright flash of light occurred in the night sky directly above us, I think only a couple of us saw it.
It grew from small to large and then sort of blinked out of existence but it sort of seemed to have shrunk ever so slightly before evaporating.
If you blinked or weren't looking directly at it, you would have missed it, it couldn't have lasted longer than 2 seconds.
As for the size, when it was at it's largest, I would assume 1 to 2 inches, if you were to hold a ruler out at arms length against the night sky.

What did I see that night?