Airline drinking water safety ranking

In late December, researchers from the Center for Food as Medicine and Longevity released the 2026 Airline Water Study, ranking 10 major US airlines on the quality of water provided onboard. The study focuses on water available through faucets on board, not bottled water service.

To assess each airline's water quality, the team collected 35,674 water samples over a three-year study period from the 1st of October 2022 to the 30th of September 2025. Each airline was then assigned a “Water Safety Score” from 0 to 5, based on five weighted criteria, including violations per aircraft and maximum contaminant level violations for E. coli. The team noted that any score above 3.5 indicates that the airline has "relatively safe, clean water and earns a Grade A or B."

Airline water safety scores:

Major U S Carriers

RANK AIRLINE SCORE GRADE
1 Delta Airlines            5.00       A
2 Frontier Airlines        4.80       A
3 Alaska Airlines          3.85       B
4 Allegiant Air              3.65       B
5 Southwest Airlines    3.30      C
6 Hawaiian Airlines      3.15      C
7 United Airlines           2.70      C
8 Spirit Airlines             2.05      D
9 JetBlue                      1.80      D
10 American Airlines    1.75      D

After analyzing all the samples, the researchers named Delta Airlines as having the "safest water in the sky" after scoring a perfect 5 on the assessment. It was followed closely by Frontier Airlines, which scored 4.80, placing it well within the Grade A category. Alaska Airlines rounded out the top three with a score of 3.85 (Grade B). According to the team, the worst-performing major airlines were American Airlines and JetBlue, both of which received a D grade.

As for what you should take away from these findings, the researchers said you should "never" drink any water on a flight unless it came from a sealed bottle. That includes coffee or tea made with tap water. Additionally, you should not wash your hands with tap water; use "alcohol-based hand sanitizer containing at least 60% alcohol" instead.

And if you're wondering how airplane water can get so nasty, the researchers explained that unlike your municipal water, which has a "continuous flow and regular monitoring," aircraft water systems are often stagnant (think of times between flights) and experience temperature variations from sitting on the ground to takeoff, cruising, descent, and landing, creating environments "conducive to biofilm formation and microbial proliferation."

I looked into results for Australia but could only come across the below.

There's no single definitive ranking for Australian airline drinking water safety, but generally, major carriers like Qantas and Virgin Australia follow strict Australian standards with regular checks, while Jetstar uses bottled water only on many short flights, indicating varied approaches; however, it's often recommended to opt for bottled water or avoid airplane tea/coffee due to potential tank hygiene issues, as some cabin crew suggest.

 
Key Considerations: 

• Regulations & Testing: Airlines must comply with strict aviation safety standards, including water quality, with regular testing of onboard tanks and ground supply.

• Chlorination: A small amount of chlorine is typically added to water tanks to prevent bacterial growth, making it generally safe but sometimes affecting taste.

• Tank Hygiene: While regulations exist, the cleanliness of water tanks and the pots used for tea/coffee can vary, leading some crew to prefer bottled options