Passenger Has a Headache and You Feel Tired Mid-Flight: What Should a Private Pilot Suspect?

The Silent Emergency You Cannot Smell or See

Carbon monoxide is one of the most dangerous threats in a piston aircraft cockpit precisely because it gives you almost nothing to work with. It is colorless, odorless, and tasteless — you will never detect it through your senses alone. By the time you notice something is wrong, your judgment and reaction time may already be compromised. This is exactly why the FAA dedicates specific attention to CO poisoning recognition and response in the Pilot's Handbook of Aeronautical Knowledge (PHAK, FAA-H-8083-25), and why your designated pilot examiner is likely to test you on it.

In the scenario above — a passenger complaining of headache and drowsiness while you feel unusually fatigued — carbon monoxide poisoning should be your first suspicion, not your last. Many pilots make the mistake of attributing those symptoms to a long day, poor sleep, or a passenger who simply did not eat enough before the flight. That instinct to rationalize is dangerous. When two people in the same aircraft develop similar symptoms at the same time, the environment they share is the common variable, and that environment may be slowly poisoning both of you.

Where the Carbon Monoxide Actually Comes From

Understanding the source of CO in a piston aircraft makes the response actions far more intuitive. Most general aviation aircraft use a combustion-based cabin heater that draws air from the area surrounding the exhaust manifold. Under normal conditions, that system works fine. But exhaust systems develop cracks and leaks over time, and when they do, exhaust gases — including carbon monoxide — can be pulled directly into the cabin air supply along with the heat.

This is why the cabin heater is the primary suspect in any CO incident aboard a piston aircraft. The cruel irony is that pilots are most likely to run the heater on longer cross-country flights at altitude, precisely when fatigue might already be creeping in and masking early symptoms. A CO detector mounted in the cockpit — available inexpensively at most aviation retailers — is one of the most valuable pieces of safety equipment you can carry. Some examiners will ask whether you have one and what it looks like when it triggers. Know your equipment.

Immediate Actions: What You Do in the Next 30 Seconds

Once you suspect carbon monoxide poisoning, your response must be fast and deliberate. The PHAK is clear on the priority actions, and your examiner will want to hear them in a logical sequence.

• Turn the cabin heater completely off. This is the single most important immediate action. Leaving the heater on even partially continues to pump contaminated air into the cockpit. Do not turn it down — turn it off entirely.
• Open all fresh air vents and windows. This is where pilots sometimes hesitate, thinking the outside air is too cold or uncomfortable. Discomfort is irrelevant. Fresh air is the antidote. Flushing CO from the cabin requires immediate ventilation, and cracked windows or partially opened vents will not do the job effectively. Open everything available to you.
• Use supplemental oxygen if available. Oxygen accelerates the elimination of CO from your bloodstream. If your aircraft is equipped with it, use it without delay for both yourself and your passenger.
• Declare an emergency. A passenger who is drowsy or complaining of symptoms is potentially incapacitated, and you yourself may be more impaired than you realize. Squawk 7700, contact ATC, and state your situation clearly. This is not a judgment call — it is the correct procedure, and failing to declare an emergency in this scenario is a mistake examiners notice.
• Divert to the nearest airport for an immediate landing. Do not continue to your destination. Get the aircraft on the ground, get both occupants into fresh air, and seek medical attention.

After landing, report the incident so the aircraft can be grounded and inspected by a qualified mechanic. An exhaust leak that poisoned two people once will do it again if left unaddressed.

Why This Question Matters Beyond the Checkride

Carbon monoxide poisoning has contributed to fatal general aviation accidents. The insidious nature of the hazard — impaired judgment masking the very awareness needed to recognize the emergency — makes it uniquely lethal. Pilots who have studied this topic and rehearsed the response actions are measurably better prepared to act correctly when cognitive function is already degraded.

Your examiner is not asking this question to trick you. They are asking it because the answer reflects whether you understand the systems in your aircraft, the physiological threats in your environment, and the decision-making framework required to protect your passengers. A confident, complete answer demonstrates all three. Know the source, know the symptoms, know the steps — and know that speed matters when the air in your cockpit is working against you.

If you want to practice questions like this in a realistic oral exam format, try SimulatedCheckride.com.