What medical conditions can stop you from flying?

September 21, 2025 •

4 min read

The cabin air pressure on a commercial flight is equivalent to being at an altitude of 6,000–8,000 feet above sea level, which affects a passenger's body in several ways. This makes understanding what medical conditions can stop you from flying crucial for safe travel planning.

Quick Summary

Severe or uncontrolled medical conditions such as active heart disease, unstable respiratory illnesses, recent surgery involving trapped gas, certain infectious diseases, and severe anemia are primary reasons to postpone or avoid air travel.

Key Points

Check Stability Before You Fly: If you have a chronic condition, ensure it is stable and well-controlled before booking a flight to minimize risks from cabin pressure and lower oxygen.
Consult a Physician for Medical Clearance: For unstable conditions, recent surgeries, or infectious diseases, a doctor's assessment and formal medical clearance are often necessary to ensure safety and prevent denied boarding.
Understand Risks of Low Oxygen: Passengers with severe heart or lung diseases may be at risk from reduced cabin oxygen levels and might require supplemental oxygen during the flight.
Be Aware of Gas Expansion: Recent surgeries involving trapped gas (e.g., eye, abdominal) and ear/sinus infections are major contraindications due to pressure changes causing pain and tissue damage.
Prevent DVT with Movement and Hydration: Reduce the risk of deep vein thrombosis by staying hydrated, avoiding alcohol, and performing regular leg stretches and walks during long flights.
Postpone Travel for Contagious Illnesses: If you have a fever or a transmissible infection, delay your trip to protect fellow passengers and avoid being denied boarding by the airline.

Understanding the Physiological Impact of Flying

Air travel subjects the body to unique physiological stresses that can exacerbate certain health conditions. The lower cabin pressure and reduced oxygen levels can be problematic for some individuals. The dry cabin air and prolonged immobility also introduce specific risks.

Hypoxia: The Effect of Reduced Oxygen

At cruising altitude, the oxygen available in the cabin air is less than at sea level. For healthy individuals, this is not an issue, but for those with pre-existing heart or lung problems, the reduced oxygen (hypoxia) can strain the body and cause symptoms to worsen. This is a major reason why medical clearance is needed for some passengers.

Gas Expansion: The Impact of Pressure Changes

During ascent and descent, the air pressure in the cabin changes, causing gas trapped within the body to expand and contract. This can affect:

Sinuses and ears: Blocked passages from a cold or infection can lead to barotrauma, causing severe pain and potential damage.
Recent surgery: Trapped gas from recent abdominal, eye, or brain surgery can expand, potentially disrupting stitches or causing pain and tissue damage.
Gastrointestinal system: Trapped gas in the intestines can cause bloating and discomfort for those with recent gastrointestinal procedures.

Immobility: Risk of Blood Clots

Sitting for long periods in a confined space significantly increases the risk of developing a Deep Vein Thrombosis (DVT), a blood clot, especially in the legs. Certain conditions like a history of blood clots, cancer, and pregnancy further increase this risk.

Key Medical Conditions That May Prevent Air Travel

Several conditions may warrant postponing or avoiding air travel.

Cardiovascular Conditions

Conditions like recent heart attack or stroke, unstable angina, severe heart failure, or high-risk arrhythmias can make flying risky due to the effects of reduced oxygen. Medical clearance is often required.

Respiratory Conditions

Severe conditions such as severe COPD or asthma, unresolved pneumothorax, or recent lung surgery can be exacerbated by lower cabin pressure and oxygen levels. A fitness-to-fly test may be needed for some individuals.

Post-Surgical Concerns

Recent surgery, particularly those involving trapped gas in areas like the abdomen, head, face, eyes, and chest, requires a waiting period before flying to avoid complications from gas expansion. The recommended waiting time varies depending on the type of surgery.

Infectious Diseases

To prevent the spread of illness, you should avoid flying if you have a contagious disease such as chickenpox, COVID-19, measles, or active tuberculosis. Airlines may deny boarding if you show symptoms of illness.

Mental Health Conditions

While most mental health conditions are not a barrier to flying, unstable or acute conditions like uncontrolled psychosis or severe anxiety that makes flying impossible may require consideration.

Other Specific Conditions

Individuals with sickle cell anemia or severe anemia face increased risks from low oxygen. Recent decompression sickness after scuba diving and late-stage pregnancy (depending on airline policy and medical advice) can also necessitate postponing travel.

Comparison of Travel Risks: Stable vs. Unstable Conditions


Medical Condition	Stable/Controlled	Unstable/Acute	Risk Factor in Flight	Actions Before Flying
Heart Disease	Mild angina controlled by medication	Chest pain at rest, recent heart attack, severe heart failure	Reduced oxygen (hypoxia) increases heart strain.	Get doctor's clearance; carry medication and ECG copy.
Respiratory Disease	Mild asthma, stable COPD	Severe COPD, active infection, unresolved pneumothorax	Hypoxia and cabin pressure changes exacerbate breathing difficulties.	Fitness-to-fly test; supplemental oxygen may be needed.
Recent Surgery	Minor laparoscopic procedure (>24 hours)	Open chest/abdominal surgery (<10 days), recent intraocular gas injection	Gas expansion can disrupt sutures or cause tissue damage.	Confirm healing time with surgeon; get medical clearance.
Infectious Disease	Fully recovered, no active symptoms	Fever, rash, persistent cough, or other contagious signs	Risk of transmission to other passengers.	Postpone travel until no longer contagious; get doctor's letter.
Mental Health	Anxiety managed with medication	Uncontrolled psychosis, severe anxiety	Stress of travel can trigger episodes or disruptive behavior.	Consult psychiatrist; ensure condition is stable.

When to Seek Medical Clearance

Consulting a healthcare professional before flying is important if you have a chronic condition or have recently had a medical procedure. They can assess your fitness to fly and recommend precautions like supplemental oxygen. Airlines often require a medical information form (MEDIF) for passengers with certain conditions. The Centers for Disease Control and Prevention offers further guidance, and checking your airline's specific policies is also recommended.

Conclusion

Flying is generally safe for most, but the cabin environment poses risks for individuals with certain health conditions, including heart, lung, recent surgery, infectious diseases, and mental health issues. Discussing travel plans with your doctor, understanding the potential risks, and taking necessary precautions are key for a safe and comfortable journey. Prioritize your health and defer travel if your condition is unstable or potentially contagious. For more information, the American Academy of Family Physicians website is a useful resource at https://www.aafp.org.

Frequently Asked Questions

If you have a severe cold or sinus infection with significant congestion, it is advisable to postpone your flight. Pressure changes can cause painful ear or sinus barotrauma. Using decongestants can help for milder cases, but if you have a fever, it's best to wait until you are fully recovered.

This depends on the severity of the event. For a low-risk heart attack, some guidance suggests waiting 3 to 10 days post-event, while a stroke might require a 1 to 2-week waiting period. Always consult your cardiologist or neurologist for a personalized timeline and medical clearance.

For mild to moderate COPD, flying may be possible, but severe COPD can pose significant risks due to lower cabin oxygen. You may require a 'hypoxic challenge test' to determine if you need supplemental oxygen during the flight. Always discuss your travel plans with your doctor.

Yes, especially if the procedure involved trapping gas inside the body (e.g., eye, abdominal, chest surgery). The trapped gas expands at altitude and can cause complications. Waiting periods vary, so follow your surgeon's specific post-operative advice.

You should not fly if you are actively contagious. This prevents transmission to other passengers. If you've recently had a contagious illness like chickenpox, you may need a doctor's note confirming you are no longer infectious.

Most airlines allow travel during an uncomplicated pregnancy up to a certain point (often 32-36 weeks). Beyond this, or if you have a high-risk pregnancy, you will need a medical certificate from your doctor. Always check your airline's specific policy in advance.

To reduce the risk of deep vein thrombosis (DVT), stay hydrated, avoid excessive alcohol, wear loose clothing and consider compression stockings. Get up and walk around the cabin every hour, and perform seated leg exercises throughout the flight.