In the paper the development of a fully electronic transmit-receive phased-array antenna system in Ku-band for aircraft communications via satellite is presented. Particular emphasis has been placed in the improvement of the following key elements: a dual-polarization self-diplexing radiating element, a transmit/receive active module with full polarization agility based on a digital vector modulator and a SiGe multinode MMIC. The optimized antenna elements enable a significant improvement towards the realization of a future affordable commercial product for satellite communications.