Unreal is used for FPSes, as well as 2.5d side scrollers like unmechanical. People were building flight sims with the Quake 1 engine (Airquake). Simply having a 3D engine doesn't shoehorn you in to a particular style of play.
Not just Quake. A little over a decade ago I worked on a vehicle-based total conversion for the original Unreal Tournament that centered on air combat.
One such infrastructure is the Internet itself. If such a hypothetical AI were savvy, it could create a large measure of influence over social networks through impersonation and massed artificial identities. Were it clever enough, it could mask its own incursions into physical space - effectively remaining undetected while vulnerable to human interdiction.
This is all assuming we could comprehend the motives of such an entity...
Still using an older (read: "Pre-Unity") version of Ubuntu? It’s time to upgrade.
Indeed it is. Here's a better suggestion.