Array antennas which are integrated onto structures of aircraft and unmanned aerial vehicles (UAVs) are subject to unsteady aerodynamic loads. Mechanical forces and these aerodynamic loads will cause deformation of the antenna supporting structure. As a consequence, the positions and orientations of the elements of the phased array antenna change. The relative phases of the respective signals feeding the antennas will vary, and as a consequence the antenna radiation pattern is affected: the main beam direction can change and the beam width and/or side lobe levels can increase. The influence of deformations and vibrations will be most significant on array antennas, which are large in terms of wavelength (high gain antennas). The objective of the present paper is to present some applications of such array antennas, and to discuss the effects of deformations and vibrations on the performance of array antennas, and to describe technology to counteract these effects by means of adaptive or synthetic beam forming.