The Silent Ally: Using Oxygen While Flying Pilot-in-Command

by Chris Horsten, Director, Canadian Light Sport Aircraft Association

Chris Horsten is the founder and director of the Canadian Light Sport Aircraft Association and the owner of Sport Aircraft Canada, a company that sells aeroplanes and accessories. Chris holds both a Canadian and an American Private Pilot license, with over 800 hours of flight time in general aviation and light sport types of aeroplanes, including tail-wheel and retractable gear. Chris is part of several Transport Canada working groups, together with his wife Melaya. Between them, they are members of all major associations and active within them, exhibiting at many shows and promoting the light sport aircraft industry.

Flying a small airplane offers unmatched freedom and adventure, but as altitude increases, so do the physiological demands on the body. Hypoxia—a condition caused by insufficient oxygen in the bloodstream—can silently impair a pilot’s judgment, reaction time and decision-making long before noticeable symptoms arise. Using supplemental oxygen, even below Transport Canada (TC) or Federal Aviation Administration (FAA) mandated altitudes, provides a significant edge in maintaining peak mental clarity, physical performance and overall safety. Whether you’re cruising at 10 000 ft or tackling a night flight at lower altitudes, oxygen is a simple yet powerful tool to enhance situational awareness, reduce fatigue and ensure that every flight remains as safe as it is enjoyable. This article is geared towards pilots of unpressurised general aviation aircraft.

Canadian Aviation Regulation (CAR) 605.32 states that above 10 000 ft but not exceeding 13 000 ft ASL, crew members must wear an oxygen mask for any portion of the flight exceeding 30 minutes. For operations above 13 000 ft ASL, both passengers and crew are required to use supplemental oxygen. The Federal Aviation Regulations (USA) (FARs) mandate similar yet reduced requirements.

This is similar to the US requirements for general aviation (14 CFR § 91.211). The required minimum flight crew must use supplemental oxygen for any portion of the flight exceeding 30 minutes at altitudes above 12 500 ft Mean Sea Level (MSL) up to and including 14 000 ft MSL. Above 14 000 ft MSL, the required minimum flight crew must use supplemental oxygen during the entire flight time at these altitudes. And above 15 000 ft MSL, each occupant of the aircraft must be provided with supplemental oxygen.

Unfortunately, the stories for oxygen deprivation incidents that didn’t result in a fatal accident doesn’t always make it into the usual social media or news outlets. There are likely thousands of situations which ended well but could have resulted in a preventable incident. If running out of fuel is an embarrassing cause for an accident, then hypoxia due to deliberate or even accidental neglect is likely a close second. It is no laughing matter when it results in injury, aircraft damage or death.

Some possible factors that may contribute to a hypoxia situation include:

• many new higher flying aircraft designs utilizing turbo-charged engines;
• increased range due to efficient engines and airframes;
• Electronic Flight Instrument System (EFIS) and autopilots;
• modern Instrument Flight Rules (IFR) equipment;
• pilots with unknown physiological conditions;
• heart disease, high cholesterol and high blood pressure;
• smoking or vaping;
• alcohol or drug use; and
• age and overall fitness.

For general aviation (GA) pilots of new small unpressurized aircraft, the opportunity for making use of the added range and altitude is compelling. Recreational aircraft become real tools for personal and business travel. The regulations are designed to mitigate the risks of hypoxia and ensure the safety of flight operations at higher altitudes. However, under what circumstances might these requirements be inadequate for your specific situation?

For this article, let’s focus on the physiological impact of oxygen deprivation compared to the demands of flying at high altitude.

An FAA study reported the following results for pilots of good general health. The study included 20 private pilots divided into a test group and a control group, and it simulated cross country flights at altitudes of 8 000, 10 000 and 12 500 ft. The hypoxia group breathed a lower oxygen mix to simulate higher altitudes, while the control group were given compressed air.

Their findings showed that pilots in the hypoxia group made significantly more procedural errors during cruise flight at 10 000 ft and during descent and approach phases from 10 000 ft and 12 500 ft, compared to the control group. These errors included incorrect altitude and heading changes, improper checklist usage and miscommunications with air traffic control (ATC).

Significant differences were observed between the hypoxia group and the control group in oxygen and carbon dioxide partial pressures, heart rate and blood oxygen saturation, confirming the physiological impact of mild hypoxia.

Research shows that cognitive impairment begins at even lower altitudes. At even 8 000 ft, the partial pressure of oxygen in the blood is reduced, leading to mild hypoxia in some individuals. Early symptoms, such as subtle cognitive impairments, reduced reaction time and diminished decision-making ability, can occur without the pilot being fully aware of them. Tasks requiring vigilance, multitasking or rapid problem-solving (common in aviation) are especially vulnerable to these effects. Thanks to the availability of ATC recordings, there are recordings that show the gradual cognitive decline of a pilot.

There are many compelling reasons to consider using oxygen at 8 000 ft when acting as Pilot-in-Command (PIC). These include enhanced safety, cognitive performance and physiological well-being.

1. Individual variability in hypoxia susceptibility: Not all individuals respond to altitude the same way. Factors such as age, physical fitness, sleep quality, hydration and pre-existing conditions (e.g., anemia or smoking history, obesity) can make some pilots more susceptible to hypoxia even at moderate altitudes. Using oxygen proactively eliminates this variability, ensuring consistent performance. As pilots age, their metabolism and cognitive functions can diminish, resulting in a reduced capacity. Aging can lead to decreased cardiac output and vascular elasticity, affecting the delivery of oxygenated blood to tissues. This can exacerbate the effects of hypoxia in older individuals.
2. Older pilots may have a diminished ability to adapt to hypoxic conditions due to lower overall physical fitness or pre-existing health conditions (e.g., cardiovascular or respiratory issues).
3. Slower recovery: With age, recovery from hypoxic episodes may take longer, and the associated symptoms, such as fatigue or confusion, might persist longer compared to younger pilots.
4. Pre-existing conditions such as hypertension, diabetes or smoking history, which are more common with age, can further impair oxygen transport and exacerbate hypoxia.
5. Fatigue and long flights: Prolonged exposure to even mild hypoxia can contribute to cumulative fatigue, making it harder to maintain focus over time.
6. Pilots operating at 8 000 ft for extended periods (common in unpressurized aircraft) may experience subtle but significant declines in performance as the flight progresses.
7. Night flying risks: At night, the human eye is particularly sensitive to oxygen deprivation. Vision starts to degrade at altitudes as low as 5 000 ft due to reduced oxygen delivery to the retina. Using oxygen at 5 000 ft at night improves night vision and enhances situational awareness in low-light conditions, reducing the risk of spatial disorientation or missed visual cues.
8. Safety margin and emergency preparedness: Using oxygen at 8 000 ft provides an additional safety margin in case of unforeseen altitude increases or emergencies that require prolonged effort or focus under stress. It also helps maintain full cognitive and physical capacity during challenging phases of flight, such as navigating turbulence, managing complex airspace or dealing with malfunctions.

Regular use of oxygen at moderate altitudes is a proactive approach to reducing the strain on the cardiovascular and respiratory systems, potentially lowering the risk of long-term health issues, like chronic hypoxia or pulmonary hypertension, for frequent flyers. It promotes overall alertness and well-being, contributing to safer, more enjoyable flying experiences.

What can you do to make your flying safer?

• Consider adding either a built-in or portable system to your aircraft if you own any aeroplane capable of higher altitude and long-range flight. Thankfully, oxygen systems for GA aircraft are becoming more widely available at the manufacturing stages of the aircraft and retrofit systems for post manufacturing to make using oxygen easier. There are two types of oxygen systems–on-demand and continuous flow. With respect to on-demand oxygen systems, these systems are only designed to provide oxygen to you when needed, such as during inhalation, and you must ensure that your system is certified for use at altitudes mandated by regulations. In contrast, a continuous or constant flow oxygen system is designed for simplicity with oxygen flowing continuously from the storage tank, through a regulator, to your oxygen mask. New systems are now being marketed which can produce on demand oxygen for two people up to 18 000 ft, and can reduce the reliance on refillable tanks. The integration of these systems into your EFIS means that O2 systems can be monitored at all times, including your own biometrics, to alert you before you succumb to a hypoxic situation.
• Buy a simple pulse oximeter. These can be purchased on the internet for under $50.00 and simply clip to your finger to display both your oxygen saturation and your heart rate. These are simple and valuable tools to help you monitor how your body is performing at higher altitudes.
• Many smart watches and fitness trackers now include oxygen and heart rate monitoring, some with alarms.
• A carbon monoxide detection system is a must have in your cockpit. Passive, disposable detectors have a shelf life but are useful to alert you to a possible problem. Newer electronic versions can be integrated with your EFIS to alarm if they go out of range.
• Aviation specific devices like ForeFlight Sentry can alert pilots of hypoxic conditions in combination with a pulse oximeter.
• If you don’t have these devices on board yet, you can count your breaths/minute, feel your pulse manually for high rate and look for signs of dizziness, confusion and shortness of breath for indication of a problem.
• Have a plan to descend to lower altitudes, and don’t be afraid to ask ATC for help.

Although not legally required, using oxygen regularly at 8 000 ft as PIC is a proactive safety measure that enhances cognitive performance, mitigates individual variability and ensures maximum alertness and decision-making capacity. By prioritizing oxygen use, all pilots, but especially aging pilots and those with less-than-average health, can significantly improve flight safety, reduce risks and set a higher standard for professionalism in aviation.