IMSAFE: Checking the Pilot Before the Flight

Before every flight, pilots spend time checking the airplane, weather, fuel, route, and operating environment. However, we sometimes forget to check one of the most important parts of the flight: ourselves.

You can have a perfectly good airplane and clear weather, but none of that matters if you aren’t fit to fly. That is where the IMSAFE checklist comes in:

I – Illness

M – Medication

S – Stress

A – Alcohol

F – Fatigue

E – Emotion

Most pilots learn IMSAFE early in flight training. Unfortunately, it can quickly become another acronym that students memorize for a written test or checkride without really thinking about what it means.

IMSAFE isn’t something you should use to convince yourself that you can fly. It is supposed to help you take an honest look at your physical and mental condition before getting into the airplane.

The Private Pilot Airman Certification Standards require applicants to evaluate their fitness for flight and apply personal minimums to an actual flight or a scenario given by the evaluator. In simple terms, you’re expected to evaluate yourself before the flight, just like you evaluate the airplane.

That responsibility doesn’t end after the checkride. Every pilot should use IMSAFE before every flight. If you wouldn’t accept a serious problem with the airplane, you shouldn’t accept a serious problem with the person flying it either.

I – Illness

One thing I tell my students is that if you don’t feel like you’re operating at 100 percent, you definitely shouldn’t be flying an airplane.

That may sound overly cautious, but flying requires more than feeling well enough to get through a normal day. You need to be prepared for the flight to become more demanding than expected.

A minor illness may not seem like a big deal while you’re sitting at home. Once you’re in the airplane, that illness can affect your concentration, judgment, reaction time, and ability to handle stress. Something as simple as congestion can also become very painful during a climb or descent because of the pressure changes.

Fever, dizziness, dehydration, stomach problems, pain, and difficulty concentrating can all create problems in the cockpit. Even if the flight is supposed to be short and easy, you still need to be ready for an emergency, unexpected weather, a mechanical problem, or a change in the plan.

A pilot also can’t rely entirely on having a valid medical certificate. That certificate shows that you met the medical requirements when it was issued. It doesn’t guarantee that you’re healthy enough to fly today.

Under 14 CFR § 61.53, a pilot can’t serve as a required flight crewmember while knowing about a medical condition that would prevent the pilot from meeting the necessary medical requirements. Even during operations that don’t require a medical certificate, a pilot can’t fly with a known medical condition that would make the operation unsafe.

In other words, you’re responsible for knowing when you aren’t fit to fly.

This isn’t the time to push through an illness because you don’t want to cancel a lesson or disappoint a passenger. Missing a flight may be frustrating, but it is a lot better than realizing in the air that you aren’t physically able to handle the flight.

M – Medication

Medication connects directly back to illness. I tell my students that if you have to take medication just to feel well enough to fly, you shouldn’t fly at all.

Medication may cover up your symptoms for a while, but it doesn’t always fix the condition causing them. If that medication wears off during the flight, you may be left feeling much worse at the exact time you need to be performing at your best.

You also have to consider the medication itself. Just because something is available over the counter doesn’t mean it is safe to use before flying. Common cold, allergy, motion sickness, sleep, and pain medications can cause drowsiness, blurred vision, slowed reaction time, or difficulty concentrating.

Brand names can also be misleading. Two medications may be advertised for different problems but contain the same active ingredient. Some combination cold and allergy products contain several active ingredients, which makes it even more important to read the label.

Diphenhydramine, commonly sold as Benadryl, is a good example. Most people don’t think much about taking it because it is widely available and has been around for years. However, it is a sedating antihistamine that can impair a pilot even when the person feels awake.

The FAA’s current Over-the-Counter Medications Reference Guide lists a 60-hour waiting period after the last dose of diphenhydramine. The same guide says pilots shouldn’t fly after taking a new medication for the first time until at least 48 hours have passed without side effects.

For many medications in the FAA’s “NO GO” category, the recommended waiting period is five times the longest dosing interval after the last dose. Some medications have longer waiting periods, so pilots shouldn’t assume that one rule works for everything.

The waiting period is also only part of the decision. You still have to consider the illness being treated. A medication might no longer be affecting you, but that doesn’t mean the condition has gone away.

If you aren’t sure about a prescription or over-the-counter medication, check the active ingredients and talk with an Aviation Medical Examiner. Don’t guess, and don’t assume a medication is safe simply because you’ve taken it before.

The safest way to think about medication is simple. If the medication impairs you, the condition impairs you, or you need the medication to hide how poorly you feel, stay on the ground.

S – Stress

Stress can be difficult to evaluate because it doesn’t always feel like a physical problem. You may not be sick or tired, but your mind can still be somewhere other than the airplane.

Work, money, school, family problems, relationships, and scheduling pressure don’t always disappear when you enter the cockpit. Those concerns can continue taking up part of your attention throughout the flight.

When a pilot is under stress, it becomes easier to miss a radio call, rush a checklist, overlook something during the preflight, or become impatient when the flight isn’t going according to plan.

The FAA’s Aeronautical Information Manual explains that everyday stress can reduce alertness, interfere with judgment, and cause pilots to accept risks they normally wouldn’t accept. Stress becomes especially dangerous when it is combined with fatigue.

One question I tell pilots to ask themselves is whether they could handle a very stressful situation in the airplane on top of the stress they already have.

Could you handle an engine failure, electrical problem, unexpected weather change, difficult passenger, or another emergency without becoming overwhelmed? If the answer is no, you definitely shouldn’t go.

This doesn’t mean every stressful day automatically requires canceling a flight. It means you need to be honest about how much mental capacity you have left.

A familiar daytime flight in good weather might not require the same amount of attention as a night cross-country, instrument flight, unfamiliar airport, or flight through complex airspace. The more demanding the flight is, the more mental room you need for something to go wrong.

External pressure can make stress even worse. When a pilot feels like the flight has to happen, a delay or cancellation can start to feel like a failure. Instead of asking, “Is this still a good idea?” the pilot begins asking, “How can I make this work?”

That is a dangerous change in thinking.

Don't fail to plan, plan to fail. You should always be prepared for the flight to become more difficult than expected. If the stress you already have leaves no room for another problem, the airplane should stay on the ground.

A – Alcohol

Most pilots know the phrase “eight hours from bottle to throttle,” but that phrase doesn’t tell the entire story.

Under 14 CFR § 91.17, a person can’t act or attempt to act as a crewmember within eight hours of drinking alcohol. The regulation also prohibits acting as a crewmember while under the influence of alcohol, while using a drug that affects the person’s abilities contrary to safety, or with an alcohol concentration of 0.04 or greater.

Eight hours is only the minimum amount of time stated in the regulation. It doesn’t mean every pilot is automatically safe or legal to fly as soon as the eighth hour passes.

The FAA explains in the Aeronautical Information Manual that a hangover can continue to severely impair a pilot even after the body has eliminated the alcohol. Alcohol can also make a pilot more susceptible to hypoxia and spatial disorientation.

If the effects of a hangover are still impairing you, you can’t fly simply because eight hours have passed. A headache, nausea, dehydration, poor concentration, delayed reactions, and lack of sleep can all affect your ability to operate the airplane safely.

Alcohol also connects back to medication. If you have to take medication to get rid of the effects of a hangover so you feel well enough to fly, you definitely shouldn’t fly.

At that point, you aren’t dealing with only one problem. You’re dealing with the effects of alcohol, a hangover, possible dehydration, poor sleep, and the medication you took to cover up the symptoms.

You need to consider your complete condition, not just the clock. Being outside the eight-hour window doesn’t help if you’re still under the influence or unable to operate safely.

When there is any doubt, don’t fly.

F – Fatigue

Fatigue is no joke. It can come from one bad night of sleep, several nights of reduced sleep, a long workday, physical activity, heat, dehydration, or a major change in your normal sleep schedule.

It can also build throughout the day. You may have been completely ready for the first flight of the morning but no longer be ready for the last flight of the afternoon.

The dangerous part about fatigue is that you may not realize how much it is affecting you. You can believe you’re operating at full capacity while your reaction time, memory, judgment, and decision-making have already started slowing down.

That slowdown may appear as a missed radio call, forgotten checklist item, poor fuel decision, rough landing, or trouble adjusting when the original plan changes.

The Aeronautical Information Manual describes fatigue as one of the most dangerous hazards to flight safety because pilots may not recognize the problem until serious mistakes have already been made.

Fatigue is especially important for instructors and pilots who spend long days in the airplane. Heat, turbulence, repeated takeoffs and landings, student errors, radio communication, and constant decision-making steadily use up your mental energy.

I think pilots sometimes focus too much on whether they can stay awake. Staying awake isn’t the same as being ready to fly. The better question is whether you can still think clearly and react quickly if the flight suddenly becomes difficult.

Caffeine may make you feel more alert for a while, but it doesn’t replace sleep. It also doesn’t erase several days of accumulated fatigue.

This is where personal minimums can help. A pilot might establish a minimum amount of sleep before flying, a maximum duty day, a limit on consecutive lessons, or a rule against flying at night after working all day.

These limits are easier to follow when you establish them before you’re tired and trying to justify one more flight.

E – Emotion

Emotion and stress are closely related, but they aren’t exactly the same. Stress often divides your attention, while a strong emotion can completely change the way you look at a situation.

An argument, death in the family, breakup, job problem, financial issue, or other major event may make it difficult to give the flight your full attention. Anger, sadness, anxiety, and frustration can all affect judgment.

Positive emotions can also create problems. Excitement may make a pilot just as willing to overlook risk.

A student might be determined to complete a first solo, long cross-country, or checkride after spending weeks preparing for it. A private pilot may feel pressure to complete a trip because passengers are excited or an important event is waiting at the destination.

In those situations, the pilot may begin ignoring information that points toward delaying or canceling. It may not be intentional. The desired outcome has simply become more important than the conditions support.

An emotional event doesn’t automatically make every flight unsafe. You need to decide whether that emotion is controlling your attention, affecting your judgment, or making you more willing to accept risk.

If you can’t separate the situation on the ground from the flight and give the airplane your full attention, delaying the flight is the right decision.

When the Risks Start Adding Up

One of the biggest mistakes pilots make with IMSAFE is looking at each letter by itself. These risks often connect and build on one another.

An illness may lead to medication. The illness and medication may interfere with sleep. Poor sleep leads to fatigue. Fatigue makes stress harder to manage. External pressure then gives the pilot a reason to accept all of it.

Each problem may seem minor by itself. When several are combined, they can remove nearly all the safety margin the pilot would normally have.

Imagine a private pilot preparing for an afternoon cross-country. The weather is VFR, the airplane is airworthy, and the route is familiar. However, the pilot only slept five hours because of work, has allergy symptoms, took a combination cold and allergy medication that morning, and has a family member waiting at the destination.

It would be easy to justify each problem:

The symptoms are only allergies.

The medication didn’t require a prescription.

The pilot has flown while tired before.

The weather is legal.

Someone is waiting at the destination.

Looking at each item separately makes the flight easier to justify. Looking at the complete situation shows illness, medication, fatigue, and external pressure all working together.

The airplane may be legal to fly, and the weather may be good enough, but that doesn’t mean the entire flight is a good idea.

Personal Minimums Aren’t Just for Weather

Pilots often think of personal minimums as weather limits. While weather is a major part of them, personal minimums should also include the pilot’s condition.

You might establish a minimum amount of sleep before flying, a longer waiting period after drinking alcohol, a maximum duty day, or a rule against flying while adjusting to a new medication.

These limits should be established before a specific flight gives you a reason to weaken them.

You should also adjust them to the type of flight. A short daytime flight in familiar airspace doesn’t create the same workload as a night cross-country, an instrument approach, or a flight in an unfamiliar airplane.

Your goal shouldn’t be to have just enough ability to complete the flight if everything goes perfectly. You need enough left to handle the worst reasonable situation that could happen.

Making IMSAFE Part of Every Flight

IMSAFE works best when it is used early in the planning process. Waiting until you’re standing beside the airplane with passengers watching makes it much harder to make an honest decision.

Before every flight, ask yourself:

• Is there anything affecting my physical condition?

• Am I taking medication, and what condition am I treating?

• Is stress taking my attention away from the flight?

• Am I completely free from the effects of alcohol?

• Have I had enough rest for the flight I’m planning?

• Is emotion affecting my judgment?

Then look at the complete picture. Don’t stop after deciding that each individual problem seems small.

Not every IMSAFE concern requires completely canceling the flight. You might delay the departure, shorten the flight, wait until you’re better rested, bring another qualified pilot, or use another form of transportation.

Whatever change you make needs to actually reduce the risk. It shouldn’t be another way to convince yourself to continue with a flight you already know you shouldn’t make.

Final Thought

IMSAFE isn’t valuable because pilots can remember what each letter stands for. It is valuable because pilots are often the hardest part of the flight to evaluate honestly.

You can inspect an airplane, read a weather report, and calculate the fuel required. Your own condition isn’t always as easy to measure. Illness, medication, stress, alcohol, fatigue, and emotion can slowly reduce your performance without giving you one clear reason to stop.

That is why the IMSAFE checklist needs to be more than a checkride acronym. It should be an honest go or no-go decision before every flight.

Sometimes that decision will confirm that you’re ready to go. Other times, it may require a delay, change in the plan, or decision to stay on the ground.

Always err on the side of caution. "You would rather be on the ground wishing you were in the air than in the air wishing you were on the ground."