Sentinel Majors are artificial flying constructs designed by the Forerunner and serve on the Halo Installations.
They have the same basic design as the Sentinel, with three notable exceptions. One is the gold-colored armor plating replacing the normal silver-colored armor plating. Whether this is simply a color difference or a different armor alloy altogether is unknown. The second difference is that the Sentinel Majors are armed with Advanced Sentinel Beams that fire blue-colored lasers instead of the weaker orange-colored beams that normal Sentinels use. The third is the Sentinel Major's energy shielding, which can absorb more damage than a normal Sentinel.
They were only observed on Installation 05.