A telecommunications antenna system for use with an aircraft is described that includes an aperture that is mounted at an angle relative to the horizon plane that does not change during system operation. Additional angle of elevation for adjustment of azimuth is provided by electronic means, such as a Rotman lens, while rotation within the horizon plane is provided by a rotating mechanism. Also disclosed is a radome for use with such an antenna system, which is provided dimensioned to accommodate the at a large value of the mounting angle and which can be trimmed to accommodate the system at smaller values of the mounting angle in order to minimize the impact on aircraft aerodynamics.