5-6: High-Altitude Jumps 
A high-altitude skydive is a jump made at or above 15,000 feet mean sea level (MSL) but lower than 18,000 feet MSL. MSL is not to be confused with AGL (above ground level) or the drop zone’s elevation.
USPA does not provide recommendations for skydiving at and above 18,000 feet MSL since it is outside of sport-parachuting altitudes. Those who do opt to skydive at or above these altitudes should seek outside expertise and use specialized oxygen equipment. The jumpers must develop procedures for the specific jump or event, as well as procure specialized equipment and support.
Skydives from altitudes higher than 15,000 feet MSL present participants with a range of important considerations, since reduced atmospheric pressure, decreased partial pressure of oxygen, environmental factors including temperature, and higher winds greatly increase the level of risk.
According to FAR 91.211, each occupant of the aircraft must be provided with supplemental oxygen at cabin pressure altitudes at or above 15,000 feet MSL. Hypoxia is a medical condition that develops when there is not enough oxygen in the body's tissues and is the most immediate concern between 15,000 ft MSL and 18,000 ft MSL. Hypoxia can result in impaired judgment and motor function and eventually cause unconsciousness or even death. All participants involved in the jump will benefit from familiarization training that covers the oxygen equipment being used, aircraft drills, and information about the physiological conditions encountered when exposed to reduced atmospheric pressures. Undergoing hypoxia-recognition training that allows the simulation of objective and subjective signs and symptoms of hypoxia is also extremely beneficial.
C. Equipment
In the event of a malfunction in the primary oxygen system, a backup oxygen system should be available on board the aircraft. Each aircrew member and skydiver will have access to their own oxygen mask or nasal cannula, although a common central oxygen bottle and regulator system may be used as a supply.
D. Oxygen-Use Procedures
Warning: Oxygen explosively accelerates burning! To prevent damage to aircraft and equipment and injury to persons from oxygen-fed flash fires, the aircraft should be electrically grounded during all ground practice. No smoking should be permitted in the vicinity of the aircraft, either on the ground or aloft, while oxygen equipment is on board.
Oxygen-use procedures will vary with the equipment used, but the following are basic:
- All participants should don masks or nasal cannulas with a positive flow of oxygen prior to exceeding 15,000 feet MSL. Oxygen flow should be continuous throughout the remainder of the climb and jump run and should be monitored continuously via gauges or visual flow indicators. The aircraft operator should ensure sufficient oxygen supply for all exposures above 15,000 feet MSL, including supply for extended delays at altitude.
- Prior to exit, jumpers should stay on oxygen for as long as possible, removing their masks or cannulas at the “climb out” or “exit” signal. Participants should rehearse these procedures on the ground in order to ensure a safe climb to altitude and aircraft exit.
- In the event of an aborted jump run, all participants will ensure the re-donning of their own oxygen equipment, assist others and await further instructions from the aircrew.