This paper presents a multibeam planar horn array covering a full azimuth direction. The proposed antenna array is made of compact substrate integrated horns. The beamwidth of a single horn is 30°. Therefore, the full azimuth coverage can be achieved by using twelve horns. The radiation patterns of the neighboring horns intersect with each other at - 3 dB beamwidth. This antenna array has a wide relative bandwidth up to 32% in Ka-band. In the operating frequency, all the beams are well isolated to each other by a low mutual coupling below -45 dB. The proposed array is fabricated using a single-layer printed circuit board with a thickness of 1.5 mm. The compact size makes the integration of this array easy. Additionally, the omnidirectional pattern of the array can be used to support high speed beam tracking and overcome blockages for unmanned aerial vehicles.