I believe it not probs, had it happen to me and a friend witness the spark. conditions were a bit spoky with that lightning feel to the air and low cloud and wet. not sure i buy the dust theory but then again this can happen.
However (I've not watched the movie) that is a crock of &$*(. You can only build up a charge in the kite when off the water as you are constantly earthing the static charge on the water.
Think school, think vadnagraph(?) generator and you had to stand on a plasic sheet to make it work.