SKYWRITING: an advertising medium in which airplanes spell out names and slogans in the sky by means of the controlled emission of thick smoke. A technique first developed (1922) by J. C. Savage, an English aviator. Letters are a mile high and a mile wide. They are formed by the movements of skywriting airplanes equipped with the smoke-emitting systems. Exhaust heat is used to turn a special mix of paraffin oil into thick white smoke, which is discharged through the exhaust system. The "skywriting" is done at heights at 10,000 to 15,000 ft and is best only in cloudless skies in which there is light to moderate wind. Writings are commonly made for skywriting over a designated area, ., a racetrack, fair, beach, or concert, and for a specified day and time. Skytyping, is a more modern form of skywriting, involves the use of five to seven planes. They fly parallel to each other in formation and equidistant courses as nearly in perfect unison as possible. The message is arranged on a master computer, and as the planes fly in line, electronic signals emit the smoke.