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The certification process for aircraft ground anti-icing fluids involves flat plate wind tunnel aerodynamic flow-off tests. This test method was developed in 1990 from flight and wind tunnel tests results on full scale and model airfoils, and flat plates; the resulting lift losses were then correlated to the Boundary Layer Displacement Thickness (BLDT) on a flat plate. This correlation was made for Type II fluids existing at the time. Since the introduction of Type IV fluids in 1994, with significantly longer anti-icing endurance times, the same test procedure was applied. However, Type IV fluids are generally more viscous than Type II fluids of the same concentration. At the FAA's request, a study was undertaken to see if aerodynamic certification testing should be different for Type IV fluids as opposed to Type II.