A Coalition Fleet refers to a joint Alliance and Foundation attack force, consisting of any combination of warships from the Alliance, Gudersnipe, or Alliance member worlds. The term was first coined at the begining of the Second Age when warships from the Gudersnipe Foundation began running manuevers with ships from the then newly-formed Unity Earth Sphere Alliance. At the time, there were no ships belonging to the Alliance itself, but rather from it's member worlds.
At first, it was argued that Alliance ships should be organized into seperate battle groups. However, frequent and small operations within the still-stabalizing Alliance and throughout the area known as joint space often required small numbers of Alliance member world ships to work side-by-side with the Foundation.
Command was a heated issue, as obviously someone had to be in charge of a joint operation, and the Foundation reused to place it's ships under the command of Alliance leaders. It was argued, and reasonably so, that since war was "the Foundation's buisness", it made more sense to let them run things.
For the first few decades of Coalition Fleet movments, there were many tense times. The Alliance was just starting to build ships of it's own, and form a complete military force under the direct command of officers who had no higher alegence.
Since most Alliance military academies were, at the time, run by experienced soldiers from the Foundation, it didn't take long to pass a law within the Alliance that all Coalition operations would be under the command of the ranking Foundation officer.
A few acceptions are made when Gudernsipe ships are providing support for Alliance capital ships, but even after the Alliance academies were taken over by Alliance officers, the ordinance still held.