Why shouldn't you drink tea or coffee on a plane?

October 7, 2025 •

4 min read

According to a 2019 study from the Hunter College NYC Food Policy Center, several major and regional U.S. airlines received low scores for water quality, with tests revealing the presence of E. coli and coliform bacteria. The hot beverage served onboard is often made with this same potable water, raising significant hygiene concerns for passengers.

Quick Summary

Airline hot beverages pose health risks due to questionable water quality from onboard tanks. Combine this with the dehydrating effect of caffeine at altitude, and you have compelling reasons to skip the coffee or tea. Staying hydrated with sealed bottled water is the safer, healthier choice.

Key Points

Questionable Water Quality: Onboard water tanks used for brewing are prone to bacterial contamination, including coliform and E. coli, according to several studies.
Increased Dehydration: The low-humidity cabin environment combined with caffeine's diuretic effect leads to faster and more pronounced dehydration, causing fatigue and headaches.
Sleep Disruption: Caffeine can significantly interfere with in-flight sleep patterns, which can worsen jet lag and reduce restfulness upon arrival.
Crew Avoidance: Many flight attendants have confirmed they avoid drinking the hot beverages made with airplane tap water due to concerns over tank cleanliness.
Digestive Discomfort: Cabin pressure changes combined with the acidity of coffee can increase bloating and cause stomach upset during the flight.
Safer Alternatives: Opt for sealed bottled water, canned beverages, or bring your own reusable bottle to fill after security for the safest hydration.

The Questionable Source: Onboard Water Quality

For many travelers, the promise of a hot cup of tea or coffee is a comforting ritual during a flight. However, a closer look at the source of that water reveals some unsettling facts. The hot beverages served on airplanes are brewed using water from onboard tanks, not bottled water. Multiple reports and studies have raised red flags about the cleanliness of these tanks and the water they store.

Research, including a detailed 2019 study conducted by DietDetective.com and the Hunter College NYC Food Policy Center, found that many aircraft had contaminated water supplies. The study revealed varying levels of coliform bacteria, with some tests even showing E. coli contamination. While airlines are subject to regulations from the Environmental Protection Agency (EPA) under the Aircraft Drinking Water Rule (ADWR), enforcement can be inconsistent. Airlines are required to test their water and periodically disinfect and flush the tanks, but the frequency and thoroughness of this process have been questioned. The issue is further compounded by the way water is transferred to the aircraft, with the study noting that contamination can occur from transfer equipment like hoses and water trucks.

Many flight attendants, the very people who serve these beverages, have long-standing reservations about the onboard water. Citing concerns about infrequent tank cleaning and the potential for contaminants, many crew members actively avoid drinking the coffee and tea themselves. For those who have witnessed the interior of these water tanks, the switch to bottled or canned drinks is a simple precaution against potential illness. While some aviation insiders argue that boiling the water should kill bacteria, the effectiveness is not guaranteed, especially with varying boiling points at high altitude and the potential for post-boil contamination from a dirty dispenser.

The Dehydration Double-Whammy

Even if the water quality were impeccable, the caffeine content in coffee and some teas presents another major problem for air travel. The low-humidity environment of an airplane cabin is inherently dehydrating; moisture is constantly being pulled from your skin, eyes, and lungs. Caffeine is a diuretic, meaning it increases the rate of urination and accelerates fluid loss from the body. Drinking a caffeinated beverage on a flight is essentially a recipe for amplified dehydration, which can lead to a host of uncomfortable symptoms.

Signs of in-flight dehydration can include headaches, dizziness, dry mouth, and fatigue. These symptoms are often misattributed to other factors of air travel, such as jet lag or cabin pressure. By choosing coffee or tea, you exacerbate these issues instead of mitigating them. The constant need for bathroom breaks caused by caffeine's diuretic effect is also inconvenient in the small, often-occupied confines of an airplane.

The Negative Effects of Caffeine on Sleep and Anxiety

For many, flying is a stressful experience, and long-haul flights require passengers to get some sleep to arrive refreshed. Unfortunately, consuming caffeine makes both more difficult. Caffeine stimulates the central nervous system, increasing heart rate and causing jitters. For individuals already experiencing anxiety related to flying, this can worsen feelings of nervousness and stress. Furthermore, caffeine has a long half-life in the body, meaning its effects can last for several hours after consumption. This can make it difficult to fall asleep or stay asleep during the flight, hindering your ability to adjust to a new time zone and making jet lag more severe upon arrival. The acidity of coffee can also irritate your digestive system, leading to heartburn, bloating, or nausea, particularly when combined with cabin pressure changes.

Comparison: Bottled vs. Tap-Based Drinks Onboard


Feature	Bottled/Canned Drinks	Tap-Based Drinks (Coffee/Tea)
Source	Sealed, commercially regulated containers.	Onboard water tanks; refilled at various airports.
Purity	High standard; factory sealed and sanitized.	Varies by airline and aircraft; potential for bacterial contamination.
Hydration	Generally hydrating (especially water).	Dehydrating due to caffeine's diuretic effect.
Caffeine	Zero (for water/juice); controlled (for sodas/energy drinks).	High (for coffee); moderate to high (for tea).
Health Risk	Very low, assuming bottle is sealed.	Higher, due to potential for bacterial contamination.
Digestive Impact	Minimal (for water).	Higher risk of digestive discomfort (acidity, bloating).

Safer and More Hydrating Alternatives

Given the potential risks, it is far safer and healthier to avoid the onboard hot beverages. Several convenient and hydrating alternatives can enhance your travel experience and ensure you arrive feeling your best. The simplest solution is to bring an empty reusable water bottle, which you can fill at a designated water station after passing through security. This saves money and provides a constant source of clean hydration. If you prefer hot beverages, consider bringing your own herbal tea bags (e.g., chamomile or peppermint) and asking for a cup of hot, sealed bottled water. Some airlines may even provide bottled hot water upon request. Stock up on sealed bottled water, canned juices, or sodas available for purchase in the terminal after security, as these are processed under regulated, sanitary conditions. Additionally, packing water-rich fruits and vegetables like cucumbers or oranges can provide extra hydration during your flight.

Conclusion: Prioritize Your Well-being at 30,000 Feet

While the sight of a flight attendant with a beverage cart can be a welcome sight, it is prudent to decline the offer of hot coffee or tea. The confluence of potentially unsanitary onboard water, the dehydrating properties of caffeine, and its negative impact on sleep and anxiety make it a poor choice for air travel. By prioritizing sealed, bottled alternatives and staying consistently hydrated, you can significantly reduce your risk of travel-related sickness and arrive at your destination feeling more refreshed and energized. Ultimately, the comfort of a mid-flight hot beverage is not worth the potential health risks. For more detailed information on the 2019 study, you can refer to the findings on the Hunter College website.

Frequently Asked Questions

While regulations are in place to ensure water quality, studies have shown that bacteria like E. coli and coliform can be present in some aircraft water tanks. Many flight attendants choose to avoid the hot beverages, suggesting there is a real risk, however small it may be.

Boiling water does kill most bacteria, but it's not a foolproof solution. Factors like the lower boiling point at high altitude, potential re-contamination from the dispenser, and the general cleanliness of the preparation area mean that simply boiling the water doesn't guarantee complete safety.

The air in an airplane cabin has extremely low humidity, often drier than a desert. This dry air draws moisture from your skin and respiratory system at an accelerated rate. Combining this with a diuretic like caffeine exacerbates the problem.

The safest options are sealed beverages like bottled water, canned juices, or soda. You can also bring an empty reusable bottle to fill with water after passing security. Herbal tea made with bottled water is a good hot alternative.

Many current and former flight attendants have publicly stated that they avoid the coffee and tea made with the plane's tap water. Concerns about water tank hygiene are the primary reason for this practice.

Yes, sealed bottled water is a safe choice. It comes from regulated commercial sources and is not stored in the aircraft's onboard tanks. Flight attendants and travel experts recommend sticking to bottled or canned options.

You can bring an empty reusable water bottle through security and fill it at a fountain near your gate. You can also purchase sealed bottled drinks or canned beverages after the security checkpoint.

Herbal tea is better because it is caffeine-free, meaning it won't cause dehydration or affect your sleep as much. However, it should still be made with sealed bottled water to avoid the hygiene risks associated with the onboard water tanks.