Skywriters

So I was on my lunch break and had the pleasure of watching 5 planes write "JOHN FROM CINCINATTI" over West Midtown. What's the deal with these guys regarding ATC? Do they fly above the Class B airspace? Who do they have to talk to on the radio? Are they considered to be flying in formation, or do they need a different callsign for each plane? What kind of aircraft are they?

They fly the North American SNJ, which was the USN version of the USAAC Texan trainer. Messages are gennerally printed at 10,000 FT.
More info here...

http://www.skytyping.com/home.htm