What needs to happen if cabin altitude exceeds FL250 and occupants are not wearing pressure suits?

When cabin altitude exceeds FL250 and the occupants are not wearing pressure suits, the appropriate action is to descend to the lowest practical altitude. This measure is critical because pressures at high altitudes can lead to hypoxia, which affects the ability of individuals to maintain cognitive and physical functions. Descending reduces the cabin altitude, thereby increasing the available partial pressure of oxygen, which is essential for the safety and well-being of the occupants.

This response addresses the immediate risks associated with high cabin altitudes and ensures that the aircraft operates within a safer environment for everyone onboard. Implementing this procedure promptly can mitigate the potential health hazards caused by decreased oxygen levels leading to loss of consciousness or impaired judgment.

The other options do not address the pressing concern of oxygen deprivation faced by occupants. Filing a report is a post-incident action rather than an immediate solution. Initiating an ascent would exacerbate the problem by increasing the cabin altitude further. Increasing cabin altitude is counterproductive as it would worsen the situation leading to increased risks of hypoxia.