This is NOT true.
ALL areas of an aircraft are pressurised.The floor of a plane is not sealed, as if it were (a large, flat surface) it would EXPLODE!
Lower holds are used to carry pets and such - I don't think they would live at FL 300. The only parts of an aircrafts airframe that isn't pressurised are the wheel wells and the condensor side of the air-conditioning units. The wings aren't pressurised by cabin pressure (but they are pressurised by pumps to get the fuel out.
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This is NOT true. ALL areas of an aircraft are pressurised.The floor of a plane is not sealed, as if it were (a large, flat surface) it would EXPLODE! Lower holds are used to carry pets and such - I don't think they would live at FL 300. The only parts of an aircrafts airframe that isn't pressurised are the wheel wells and the condensor side of the air-conditioning units. The wings aren't pressurised by cabin pressure (but they are pressurised by pumps to get the fuel out.