A fleet key is necessary to send ships through a connection to another world. You can attach as many ships to a fleet key as you like; these ships then move and fire as a unit.

Ships can be built and destroyed, but the fleet key is indestructible. In general, we use the word "fleet" throughout the game to refer to a fleet key and all of its ships, even when there are no ships at all on the key.

In addition to the five fleet keys that you own at the beginning of the game, there are several more empty, unowned fleet keys scattered throughout the galaxy. The total number of fleets is fixed in a particular game (fleet keys cannot be created or destroyed), and the exact number depends on the number of players.

As with worlds, though the precise rules of ownership are more complex, in general, you will automatically claim as your own any empty fleet keys you find at the worlds you are the first to visit.