Skydiving includes free falling (usually from an aeroplane) through the air prior to opening a parachute. Typically skydives are carried out from around 4,000m (or 12,500ft) offering 40 to 50 seconds of freefall time. Longer free fall times can be achieved by exiting an aircraft at altitudes much higher than 4,000m, but very high jumps require pressurized oxygen within the aircraft, and bottled oxygen for the diver. 