Both are a type of advertising that use aircraft to spell words in the sky by mixing paraffin oil into smoky plane exhaust.
Ever sat at the beach or an outdoor event and watched a plane writing in the sky? It was captivating, wasn’t it? You try and guess what they are going to say, waiting for the plane to be finished. The advertiser has gotten your attention longer than if you whizzed past a billboard or glanced at a newspaper page. And it probably made a more lasting impression.

That was the thinking of the Pepsi-Cola Corporation, one of the first companies to use skywriting for an advertising campaign. One of the first skywriters, Andy Stinis, flew for Pepsi-Cola from 1931-1953.

Skywriting is done by one plane that can generally write up to six characters, with a skilled pilot at times maneuvering upside down as they decide when smoke is needed for the letters. Five to seven planes are needed for longer messages (up to thirty characters) so that the entire message is visible at once.

Skytyping is a technique whereby the smoke is emitted in a series of bursts, like dots. A computer generates the master plan and electronic signals control the smoke output. The blurring of the smoke makes the desired end effect.

Night skywriting is the use of searchlights or lasers on the ground to project an image on clouds (also called cloud writing).

Fun Facts:

Most sources attribute the development of skywriting (1922) to John C. Savage, an Englishman. In that year, Captain Cyril Turner wrote "Daily Mail" over England and "Hello USA" over New York. The American Tobacco Co. then picked up the technique for their Lucky Strike cigarettes.
The first skywriting for advertising was in 1922.
April 8, 1924, Savage received a patent for “Method of producing advertising signs of smoke in the air” (US Patent 1,489,717).
A letter can be as high as one mile and take 60-90 seconds to create.
A message can stretch up to fifteen miles.
The best conditions of course are few clouds, little or no wind, and cooler temperatures. Then the letters may be seen for 30 miles in any direction and can last 20 minutes.
Writing occurs usually at altitudes from 7,000-17,000 ft.
The paraffin oil vaporizes at 1500° in the heat of the plane’s exhaust and is environmentally safe.
The skywriting that appeared in the movie, “Wizard of Oz,” was done by special effects in a tank with an oil and water mixture.
One company in New York “writes” more than 50 marriage proposals a year in the sky.

source:

http://www.loc.gov/rr/scitech/mysteries/skywriting.html


Cheers

AA