Edited: Slick's question thread.

[douglas]

Did you do some simulating of fleet battles that turn? The simulator doea a horrible job of distinguishing between fleets created in the simulator and fleets actually present in the game when it's time to get rid of them. I don't think I've seen it actually delete a fleet, but it's not at all uncommon to discover after simulating that a fleet has had all its ships removed. If you don't catch this and add them all back in, the fleet will be deleted in turn processing. For this reason, I always save before simulating with fleets and reload afterwards.