Comanche is a series of simulation games published by NovaLogic. The goal of each of these games is to fly military missions in a RAH-66 Comanche helicopter gunship, which was in development and prototyping at the time of release.
Comanche was the first commercial flight simulation based on voxel technology via the company's proprietary Voxel Space engine (written entirely in Assembly language). This rendering technique allowed for much more detailed and realistic terrain compared to simulations based on vector graphics at that time.
Source: Wikipedia, "Comanche series," available under the CC-BY-SA License.