In-game description:
"To organize stationed fleets and provide them with fuel. Number of fleets supported depends on the level of Alliance Depot, each level of Alliance Depot gives you an extra fleet slot, up to four.

An Alliance Depot allows alliance fleets to stay in orbit, in order to assist in the defense of a planet or to group with others for a larger attack. Every hour, gas is sent to these ships to keep them fuelled. Higher levels can allow up to four fleets to be stationed at the planet."

Build Time* Effect
0 -- -- -- -- 0 Alliance Fleet
1 100,000 50,000 25,000 00:45:00 1 Alliance Fleet
2 200,000 100,000 50,000 03:00:00 2 Alliance Fleets
3 400,000 200,000 100,000 12:00:00 3 Alliance Fleets
Reqs. Alliance Depot requires Shipyard Lv.6 and Fleet Command Lv.6.
Legend *modified by Robotics Factory and Nanite Factory.