sentences:  Most commercial aircraft that operate at high flight altitudes are pressurized at a maximum cabin altitude of approximately 8,000 feet.On most pressurized aircraft, if cabin pressurization is lost when the aircraft is flying at an altitude above 4.267 km (14,000 feet), compartments containing the oxygen masks will open automatically, either above or in front of the passenger and crew seats, and the oxygen masks will drop down in front of the passenger.Oxygen masks may also drop on extremely rough landings or during severe turbulence if the oxygen mask panel becomes loose.