Density altitude

In aviation, the density altitude is used to assess an aircraft's aerodynamic performance under certain weather conditions.

Furthermore, the power delivered by the aircraft's engine is affected by the density and composition of the atmosphere.

The following effects result from a density altitude that is higher than the actual physical altitude:[2] Due to these performance issues, an aircraft's takeoff weight may need to be lowered, or takeoffs may need to be scheduled for cooler times of the day.

There is an increased risk due to the high mobility of jumpers (who will often travel to a drop zone with a completely different density altitude than they are used to, without being made consciously aware of it by the routine of calibrating to QNH/QFE).

[3] Parachutes at higher altitudes fly more aggressively, making their effective area smaller, which is more demanding for a pilot's skill and can be especially dangerous for high-performance landings, which require accurate estimates and have a low margin of error before they become dangerous.