I've done hearts with initials for weddings, for example. But for longer words, the answer is skytyping. It takes five planes to skytype. They fly in a tight formation at 10,000 feet. A special transmitter on the lead plane sends information to receivers on each of the other aircraft.
Smoke puffs out in a pattern read from a perforated tape.
Wherever there's a hole, the appropriate airplane releases a puff of smoke. The result is a message eight miles long with dot-matrix style letters twice as tall as the Empire State Building. I do birthday parties, bar mitzvahs, and, of course, a lot of corporate work. When they're not in the air, the pilots sign autographs for fans of all ages. CQ Skytypers Squadron is based in Long Island, New York, but it's traveled coast to coast on skytyping missions.