Originally Posted by usmc-sgt

Real old and fuzzy info but I recall seeing an article about it. GPS linked to a smoke system where they fly a grid and it operates sort of like an old dot matrix printer. They fly the grid, the "system" handles the rest.

"The company that does this is Skywriters.
It works just as you'd expect. The airplane(s) have computer controlled smoke generators, several to a plane, and put out puffs of smoke instead of drops of ink. It's exactly like a dot matrix printer, just lower res and bigger."