The Nimitz was a payware addon for X-Plane 9. It is now included in X-Plane 10. You can download a freeware version for X-Plane 9 here : http://www.khamsin.org/ To use the Nimitz, you have to check in 'settings/rendering options' - 'draw aircraft carriers and frigates' ON Choose an airport near coastline and look for the carrier in local map. You can also open 'Aircraft/Aircraft & situations' and choose 'Aircraft carrier Approach'.
Two options : remove sceneries or remove Nimitz from these sceneries. When it's done, you can land on the aircraft carrier. It is not possible to use flight deck elevator. By the way, i'm the author of the Nimitz and also the Perry frigate and the oilrig.
Update of Boeing B-17G Flying Fortress... Version V1.3 New external 3D model, New HD Textures 4K (4096 X 4096 px), diffuse, normal and specular maps. You can download this new version on my website : www.khamsin.org Good flight !