Sky writing

Well you would probably think it would be fairly easy to find out how they form the letters in skywriting but for some reason this seems not to have made it on to the web. You can find out how high up the planes go and how big the letters are but nowhere can you find out if they do the letters flat, vertically or at an angle. Nor how they know how to form the letters. Do they work on a grid system or freehand? (Ta for having a look as well Deb.) But the news is that there is a new type of skywriting called sky typing where several planes fly parallel to each other and, controlled by a computer, they leave dot matrix style printing in their wake. I would like to see that.