What is the first symptom to address when treating a passenger who is ill or injured?

The first symptom to address when treating an ill or injured passenger is stoppage of breath. This is critical because the absence of breath indicates that the passenger is not receiving oxygen, which can quickly lead to unconsciousness and can be life-threatening. Ensuring that a passenger is able to breathe is the highest priority in emergency situations, as it directly affects their ability to survive.

Addressing breathing difficulties promptly is essential in stabilizing the person's condition. If the individual is unable to breathe, it may require immediate interventions such as performing CPR, administering rescue breaths, or using an automated external defibrillator (AED) if available and trained to do so.

The other options, although serious, do not take precedence over addressing cessation of breathing. Severe breathing issues can still allow for some oxygen exchange, while a complete stoppage of breath or no pulse indicates critical and immediate threats to life that must be remedied first.