A series of flight tests using a Boeing 737-300 jetliner were conducted in 1973-1974 at the NASA Flight Research Center (FRC)
to study the effects of wake vortices emanating from the trailing edges of the wings. The NASA study in conjunction with the
Federal Aviation Agency (FAA) was in response to the hazards being encountered when small aircraft trailing behind new large jumbojets experienced "upset" problems. The Boeing 737-300 was equipped with smoke generators for visual tracking of the wing wake vortex trail.