Near the end of the Skully Islands insurrection, the FCU military - aided by Scarface Squadron - destroyed the final enemy stronghold. Shortly thereafter, allied forces discovered that the enemy was in control of a colossal airborne aircraft carrier.
Scarface Squadron scrambled in pursuit of the Sky Fortress, but by the time they were airborne it was too late to stop the fortress on the ground. The group intercepted the fortress over the north-east ocean as it was en route to FCU-controlled territory, and a final confrontation ensued. Despite its superior firepower, Scarface Squadron destroyed the ship's engines and bridge, which led to its descent into the ocean.
The Sky Fortress is an airborne aircraft carrier capable of launching fighters and interceptors; during the battle with Scarface Squadron, it would constantly deploy F-22s to combat the threat. Whenever one was shot down, it would almost immediately deploy another in its place. In appearance, it bears a resemblance to the XB-0 Hresvelgr from Belka; however its airframe is thinner than the Hresvelgr's. Said aircraft are presumably stored within the ship, and are loaded into a catapult at its front. It is propelled by four massive engines located on its wings. The ship is armed with several air-to-air missile launchers and anti-air guns, which are placed on its wingtips and the plane's central area. The weapons, once destroyed, would seemingly respawn.