The smoke trails emitted from stunt or acrobatic planes are usually the result of injecting oil or diesel fuel into the exhaust. Often, coloring is also injected for effect.
The first time smoke trails were incorporated into acrobatic flying was in 1957 at an air show in Farnborough, England. The spectators loved the emission of the colored smoke that was used by the Royal Navy Acrobatic Team, which was known as the Black Cats. The smoke trails helped the spectators to better distinguish the maneuvers and flight paths of each airplane in the squadron as the team performed its intricate show.
Contrary to popular belief, smoke from stunt planes is not produced by ordinary combustion, nor is it a vapor trail such as those left by commercial airliners. This type of smoke effect is produced by injecting vaporized fog oil into the hot exhaust of the airplane. Various colors can be vaporized with the oil to produce colored smoke. An alternate and more modern method utilizes a smoke-producing device that can be fitted under the airplane or on the wings. These devices include various color injectors, which allow the pilot to change or mix colors while flying for maximum effect.