This report presents the results of Anti-Icing Endurance Time (AET) tests performed with unsheared samples of two certified SAE Type I aircraft deicing fluids from September 5 to October 15, 1999, at the Anti-Icing Materials International Laboratory (AMIL). Over 100 tests, including 25 calibration and 50 fluid tests, were conducted at various temperatures and icing intensities, under the six environmental conditions addressed in the holdover time (HOT) guidelines published by the SAE as part of the ARP 4737: frost (3), freezing fog (6), snow (6), freezing drizzle (4), light freezing rain (4) and rain on a cold-soaked wing (2). The results obtained demonstrate the feasibility of performing the six AET testing procedures within the prescribed accuracy and repeatability Indeed, environmental parameters in AET calibration and fluid tests were kept within the target values with variations within the allowable drifts. Moreover, AET results showed an expected inverse relationship between endurance times and precipitation rate; the shortest and longest failure times being obtained respectively under the highest and lowest icing rates. The AET test results were also compared and discussed with HOT data obtained in a parallel test set performed in July 1999 by APS Aviation (APS) at the Canadian National Research Council (NRC) facility. These tests include freezing fog, snow, freezing drizzle, and light freezing rain tests at -10 deg C, and rain on a cold-soaked wing at +1 deg C. However, their testing methods are somewhat different. AMIL failure times are systematically found to be 1 to 2 minutes shorter than APS's measured values for mean variation up to 30%, depending on test conditions. These lower failure times can be partially attributed to differences in procedures used during the test performance.