IMSAFE Checklist Acronym Explained

By Pilot Institute
Posted on March 12, 2023 - 4 minute read

IMSAFE is an acronym used in aviation to help pilots assess their physical and mental fitness before a flight.

IMSAFE is used as a “self-check” to ensure that you, the pilot, are as ready to fly as the aircraft is.

Ultimately, the safety of a flight is only as good as its weakest link. With a significant amount of accidents caused by pilot error every year, pilots must ensure they are physically and mentally fit to fly.

IMSAFE Acronym Defined

Here is what IMSAFE stands for:

I           – Illness

M         – Medication

S          – Stress

A          – Alcohol

F          – Fatigue

E          – Emotion

Let’s briefly dive into each part of the IMSAFE acronym so that you can start implementing it into your preflight today.

I – Illness

Illness (like many items in IMSAFE) is self-explanatory, with an important caveat.

In the traditional workplace, your usual call-in-sick illness, such as flu or food poisoning, will naturally also prevent you from flying.

But, when it comes to flying, you must be even more careful.

Why’s that?

Firstly, flying requires good concentration, decision-making, and the utilization of almost all of your senses. Even a light cough could prevent you from communicating on the radio, and a slight headache may be the seed that grows to be a poor decision.

Furthermore, light illnesses may be significantly worsened because of the nature of the aviation environment. The most notable example is the sinuses. Even a mild sinus infection can be excruciating during the flight due to the change in air pressure and may cause significant vertigo. Not the situation you’d want to find yourself in when you’re the only one flying.

If you’re not feeling 100%, the safest action is to delay the flight. If you’re unsure whether you’re fit to fly, consult an Aviation Medical Examiner (AME) or a doctor with experience in the aviation industry.

M – Medication

It is unwise to take medication without understanding the exact side effects you will experience. Even a simple tablet to stop a headache may make you too drowsy to fly.

Always consult your doctor or Aviation Medical Examiner about the effects of any medication you take.

S – Stress


Psychological stress can impair your ability to make good decisions and react quickly to unexpected situations.

You have a responsibility to yourself and your passengers to perform to the best of your abilities when flying. If there are external factors affecting your stress levels, it is vital that you address them before flying.

Sometimes, the nature of the flight itself may be causing increased stress.

Whether taking your check-ride or flying for the first time in a while, you should be worried if you aren’t more stressed than usual. In cases where your stress level is elevated, identifying the increased stress level will allow you to recognize and take action to manage it.

A – Alcohol

You should never fly while under the influence of alcohol. Not one drop.

A general rule of 8 hours from bottle to the throttle will serve you well, although many airlines have more stringent restrictions of 12 or 14 hours for their crew.

The Federal Aviation Regulations (FAR) state that you are not allowed to fly with a Blood Alcohol Concentration (BAC) of 0.04% or higher (the driving limit is double at 0.08%).

F – Fatigue

Fatigue is the silent killer, and has been a causal factor in numerous accidents.

Fatigue can impair your cognitive and physical abilities, making it more challenging to fly safely. From concentration to hand-eye coordination, fatigue can be a significant threat – in some cases, even more than alcohol.

Always ensure that you get high-quality sleep before flying, and avoid scheduling flights when you are likely to be tired.

E – Emotion


Emotional distress can also impair your ability to fly safely.

You must be emotionally stable when flying. If there are external factors significantly affecting your emotions, you should address them before flying.


The IMSAFE acronym is a helpful tool for pilots to assess their physical and mental readiness before a flight. Each element of the acronym – Illness, Medication, Stress, Alcohol, Fatigue, and Emotion – plays a vital role in ensuring the safety of the flight.

By being aware of these factors and taking appropriate action, pilots can reduce the risk of accidents caused by pilot error.

It’s essential to remember that the safety of the flight is only as good as its weakest link, and you should prioritize your own health and well-being to ensure a safe flight and the well-being of others.

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