This 36 second movie clip shows the Boeing 747 Wing Tip Vortex Test. As part of the overall National Aeronautics and Space Administration (NASA) study of trailing vortices -- the invisible flow of spiraling air that trails from the wings of large aircraft and can "upset" smaller aircraft flying behind -- the NASA Flight Research Center (FRC) borrowed a Boeing 747 jetliner for testing. The B-747 had been purchased by NASA for the space shuttle program and assigned to the Johnson Space Center. Six smoke generators were installed under the wings of the B-747 to provide a visual image of the trailing vortices.

Really interesting Nasa wake vortex turbolence test.