A constant-angle-of-attack-approach technique was used to measure ground effect on several low -aspect-ratio aircraft. The flight results were compared with results from constant -altitude flybys, wind-tunnel studies, and theoretical prediction data. It was found that the constantangle-of-attack technique provided data that were consistent with data obtained from constant-altitude flybys and required fewer runs to obtain the same amount of data. The test results from an F5D-1 airplane modified with an ogee wing, a prototype F5D-1 airplane, two XB-70 airplanes, and an F-104A airplane indicate that theory and wind-tunnel results adequately predict the trends caused by ground effect as a function of height and aspect ratio. However, the magnitude of these predictions did not always agree with the flightmeasured results. In addition, there was consistent evidence that the aircraft encountered ground effect at a height above one wing span.