PURPOSE: To clearly give a warning of a danger state by providing a multi- function display device for selectively forming plural displays according to the operating conditions of a life-support system, and arranging at least one display device in plural display formats.

CONSTITUTION: An aircraft includes a cabin pressurization system 300 for pressurizing inflow air to be supplied to an aircraft cabin, and a breathing device control device 304 for controlling the oxygen concentration of breathing gas supplied to a pilot. The breathing control device 304 is adapted to supply gas from one of three gas sources selected from an airborne oxygen generating device 308, an emergency oxygen source 310 and a cabin air supply pipe 312 by a selector valve 314 to a pilot. In this case, by a control processor 320 for controlling the pressurization system 300 and the breathing control device 304, the operating conditions of the system and the device 300, 304 are displayed in a multi-function display 322 by an indicating means such as an indicator indicative of cabin internal pressure, an indicator indicative of residual oxygen quantity or the like.