Fleet saving is the single most important skill for surviving in OGame. It means sending your fleet away from the planet for just the right amount of time so an attacker never finds it at home. A lost fleet can cost weeks of progress; a good fleet save makes it untouchable.
Why it matters
Your fleet is your biggest investment and the only thing an enemy can wipe out in one hit. Leaving your ships idle while you sleep or work makes you an easy target. The golden rule: never leave fleet or resources on a planet when you will be offline.
Ways to save
The most common is sending the fleet with your resources on a mission that returns exactly when you come back: to your moon, one of your planets, or "stationing" at an allied moon. You can also use expeditions (position 16 of the system) to send it "into the void" for 1, 2 or more hours.
The key is flight time: adjust the speed percentage (10% to 100%) so the round trip covers exactly the hours you will be away. Lower percentage means a longer flight and less deuterium burned.
Common mistakes
Leaving resources on the planet and sending only the fleet: the enemy takes the loot anyway. Take your metal, crystal and deuterium with you.
Sending the fleet somewhere within the enemy's Phalanx range: they can see your destination and return time and wait for you. Avoid moons and planets inside their Phalanx range.
Miscalculating the return time and arriving too early: if your fleet lands while you are still offline, you are vulnerable again.
Calculate your fleet save
Use the Flight Time calculator to find the speed percentage that brings your fleet back at the exact time you need, while showing deuterium consumption. It is the reliable way to never miss the timing.