Density altitude—pressure altitude, corrected for non-standard temperature—can be thought of as how much kinetic energy air molecules have in a given air mass. More simply, density altitude measures how thick a mass of air is and how aerodynamically viable it is. A higher density altitude corresponds to a standard air mass at a high elevation, whereas a lower density altitude could be encountered under normal conditions nearer to sea level. Density altitude is affected by three items: The air pressure, the ambient temperature, and the relative humidity of the air. This article will explain these three factors and address some performance issues associated with high-density altitude.