Experimental flight measurements were carried out in Hungary on 14 October 1988 to check the performance of the airborne microwave L-band radiometer system developed by the Space Research Group, Technical University of Budapest, for the determination of soil moisture. The results of the aircraft measurements at two different altitudes are presented. The relation between soil moisture and emissivity predicted by different dielectric models are used to estimate soil moisture. The estimated soil moisture is compared with limited ground truth soil moisture taken synchronously with flight measurements. Soil moisture and topographic maps are presented for quick-look observation of soil moisture against agricultural fields.