Seen only in Gundam 00: Awakening of the Trailblazer piloted by Setsuna F. Seiei.

Shadow Intervention Operation

During an inspection of a colony construction facility, a space shuttle bearing Marina Ismail, Shirin Bakhtiar and other inspectors came under attack by three GNX-609T GN-XIIIs from the Colony Corporation, intending to silence them. Before their shuttle could be destroyed, Setsuna F. Seiei
intervened with the Celestial Being version of the Union Flag. Using
the modified Flag to conceal his affiliation with Celestial Being,
Setsuna was nonetheless able to destroy the three GN-XIIIs, saving
Marina and Shirin from danger. After that, Setsuna retreated from the
scene, along with Lockon Stratos, who had infiltrated the shuttle and
disarmed the terrorist with a non-fatal bullet wound, via the cruise
mode of the Flag Kai.



After their mission was complete, the CB Flag was docked to Ptolemy. The fate of the unit after remain unknown.



Source:http://gundam.wikia.com/wiki/CBNGN-003_Union_Flag_Celestial_Being_Version