Fleets now have an option to place as hidden from the guild. It last for 24 hours, can be canceled at any time and the 24h reset at any time. So it can last any time long as long the player keeps resetting the timer.
On the reports it doesn’t show hidden guild fleets when you're looking at fleets in a specific galaxy. But it shows the hidden fleets when you are looking at the players fleet or guild fleets but without revealing the location.
When looking at the map or fleet details, it only shows the hidden fleets to guild members if they have a base or fleet in the region and if the fleet is moving then it is within detection time. It displays the fleet with a hidden icon.
Guild Masters and Vice GM can see the hidden fleets normally, on the map, fleet overview and reports. The fleets are displayed with the hidden icon.
An “F” (Fleet) guild permission was added to allow specific guild members to view guild members' hidden fleets alongside Guild Masters and Vice GM.
Merging/splitting fleets keep the hidden state
Note: This feature only hide fleets from your own guild. To players outside your guild this feature don't make any difference.