This work introduces a novel adaptive technique of filtering for solving the problem of interference suppression in phased array airborne radar systems. In this adaptive process, effects of the interference are suppressed (or minimized) according to a specific set of controlling parameters. This includes the target doppler shift and the interference spatial distributions. The proposed technique is referred to as adaptive space-time filter. Performance of our novel adaptive filter is investigated, evaluated, and compared to the known adaptive filter proposed by H. Ghouz in 1990 [1]. Results of simulation indicate that with adequate filter's complexity, excellent improvement in the signal-to-interference-plus-noise ratio is obtained at the filter's output. In addition, our filter has two main advantages over the one reported in [1]. First, our filter is simple and easy to implement. Second, a minimum total computational time of the adaptation process is required. This includes estimation of the interference space-time covariance matrix and updating the filter's weights as well as the required processing time. Finally, the presented filter is a robust solution to the problem of interference challenging the airborne radar systems, in particular, the strong reflection from the ground clutter sources.