CNN Anderson Cooper 360 October 29, 2015 00:05:00
We know how many are in use around the country? >> well, right now, actually, there are a pair of them in this one and another one at the same location in maryland that, by the way, at this afternoon has been grounded, obviously. this has been a major test program at the proving ground just north of washington d.c. in maryland. they have been looking at testing this and had it up for sometime trying to see how it operates and develop a track record to see how it works. whether or not they expand it, it's a very expensive effort. whether or not they expand it after today's veevents remains be s...