If you hit a friendly ship or station with your ship’s weapons, they may become hostile.

Ships you own (being flown by a pilot) can also turn friendly ships hostile with indiscriminate fire.

Weapons with an area of effect (e.g. flak turrets) can be particularly problematic. Turret fire very close to stations can also be a problem, as they will often just keep firing when target flies behind some piece of the station.

Response

Once a ship turns hostile, it’s hostile to your entire faction, not just the specific ship that triggered the reaction. Hostile ships will attack your ships and stations. If anything of yours fires back, the hostility can/will spread to other faction ships, which then also become hostile.

After a few minutes, if you don’t continue attacking, the hostile ships will return to being friendly. It’s therefore important that you take actions to prevent any of your assets from returning fire if attacked. Even if your ships/stations were attacked first, firing in self defense will escalate the hostility and you will lose reputation with the faction.

De-escalating

For ships, you can tell them to move away, or out of the sector entirely. It’s also helpful to disable ship turrets.

For stations, you can use the station information interface to disable the turrets on the station. You cannot, however, keep defense drones from launching. You can give the station an order to Recall Subordinates, but the drones will just land then quickly re-launch. It’s best to set the drone amount to zero (recovering their construction cost), wait for the hostility to end, and then setting the drone amount back up to your desired level.

When being attacked by friendly fire, you have to just go passive and take it. If you fire back, the hostility will continue and escalate. Get your ships out of harms way, wait for it cool off.

Obviously, a situation where destroyers or other powerful ships turn hostile in sectors where you own stations can end very, very badly.