An Airborne Antenna Subsystem (AAS) is presented for Ku-band airborne broadband satellite communications. The AAS employs ultra-low profile dual reflector mechanical scanned antenna to reduce the additional aerodynamic drag with high RF performance up to low elevation beam direction. The AAS achieves precise satellite tracking capability under the severe dynamic condition of airplane. In addition, the AAS achieves precise polarization tracking capability for FSS satellite transponder application. Furthermore, wide-variety of novel technologies have been developed and applied to the AAS, such as high efficiency SSPAs, ultra-thin broadband OMT, etc. The AAS gas been confirmed to achieve excellent performance, and practically operated since Spring of 2004.