A fleet in flight is technically untouchable. The real risk is leaving it docked while you're away or momentarily distracted.
On Aleryos, there are no moons or moon destruction. A fleet already in flight therefore cannot be intercepted through this kind of mechanic.
In return, attacks can be very fast. Depending on the distance and speed involved, a planet where your fleet remains docked can be attacked in as little as 2 min 30 s. So stay alert when your fleet is stationed on a planet.
To protect it, make a habit of sending it out on a flight when you log out or can't monitor your account. You can send it toward one of your own planets or toward an external target, depending on your goal.
To cover a longer absence, add a slow ship to the fleet. The overall speed depends on the slowest unit in the group, which lets you extend the travel time and adapt the flight to how long you'll be inactive.
Also use the interstellar sensors: they let you view incoming and outgoing fleets, so you can react more effectively when a fleet approaches or an important movement is underway. The “Locate in Galaxy” button centers the map on the fleet's position when clicked, if its trajectory is available. Clicking a fleet on the map opens its sensor details and keeps the usual reminder for your eligible fleets. In Settings > Server, you can hide enemy attacks in Sensors while they are still too far away; they automatically reappear there as soon as they enter the selected time window. This filter does not hide fleets on the map: attacks targeting you and Errant attacks targeting your allies remain visible there.

