A glass of water on a flight feels harmless. According to a new study, it isn’t always.
A 2026 Airline Water Study from the Center for Food as Medicine & Longevity found wide differences in the quality of drinking water served on U.S. flights — and concluded that some airlines may still be violating federal safety rules meant to protect passengers and crew.
Researchers reviewed three years of data, from late 2022 through September 2025, and scored 21 major and regional airlines on how safely they manage onboard water. The grades were based on contamination violations, E. coli risks, public disclosures, and how often planes’ water systems are cleaned and flushed.
Some airlines did well. Delta Air Lines and Frontier Airlines earned the highest safety scores, with Alaska Airlines close behind.
Others did not. American Airlines and JetBlue ranked at the bottom, while nearly all regional airlines showed problems — with GoJet Airlines the lone bright spot.
Smart Senior Daily Staff
Federal rules require airlines to regularly test aircraft water tanks and disinfect them multiple times a year. But the study also found that enforcement is weak, with few penalties issued even when airlines fall short.
For seniors — especially those with compromised immune systems — that’s worth knowing before you order coffee, tea, or water made onboard.
As we get older, the body’s built-in defenses aren’t as strong as they once were.
Weaker immune response. Aging reduces the immune system’s ability to fight bacteria like E. coli, Salmonella, and Campylobacter — all organisms linked to contaminated water.
Lower stomach acid. Many older adults produce less stomach acid, which normally helps kill bacteria before they reach the intestines. Acid-reducing medications (common among seniors) can further increase risk.
Chronic conditions. Diabetes, kidney disease, heart disease, and autoimmune disorders all make it harder to recover from infections.
Medications. Drugs such as steroids, chemotherapy agents, and immunosuppressants lower resistance to infection.
Higher dehydration risk. Water-borne illness often causes diarrhea and vomiting, which can become dangerous faster in older adults.
Bottom line: bottled water may still be the safest bet at 35,000 feet. Plus...
- Do not drink coffee or tea onboard.
- Do not wash your hands in the bathroom; use alcohol-based hand sanitizer containing at least 60% alcohol instead.
Data for all airlines (major and regional)
Airline Water Safety Scores At-a-Glance (5.00 = highest rating, 0.00 = lowest) according to published information:
Major Airlines
Delta Air Lines: 5.00 (Grade A)
Frontier Airlines: 4.80 (Grade A)
Alaska Airlines: 3.85 (Grade B)
Allegiant Air: 3.65 (Grade B)
Southwest Airlines: 3.30 (Grade C)
Hawaiian Airlines: 3.15 (Grade C)
United Airlines: 2.70 (Grade C)
Spirit Airlines: 2.05 (Grade D)
JetBlue: 1.80 (Grade D)
American Airlines: 1.75 (Grade D)
Regional Airlines
GoJet Airlines: 3.85 (Grade B)
Piedmont Airlines: 3.05 (Grade C)
Sun Country Airlines: 3.00 (Grade C)
Endeavor Air: 2.95 (Grade C)
SkyWest Airlines: 2.40 (Grade D)
Envoy Air: 2.30 (Grade D)
PSA Airlines: 2.25 (Grade D)
Air Wisconsin Airlines: 2.15 (Grade D)
Republic Airways: 2.05 (Grade D)
CommuteAir: 1.60 (Grade D)
Mesa Airlines: 1.35 (Grade F)
Airline Water Study Results
Major Airlines
Delta Air Lines
Water Safety Score: 5.00 / Grade A
Aircraft Fleet Size: 1,028
Total ADWR Violations (Oct 2022-Sept 2025): 9
Avg # of ADWR Violations per Aircraft: 0.01
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 0
Total Coliform Positive Rate: 0.47%
Indicator Positive Rate (total coliform with E. coli absent): 0.47%
Public Notices per 100 Aircraft: 0.19
Comments: Delta shows no Maximum Contaminant Level violations for E. coli and the lowest indicator-positive rate among all major airlines. Excellent performance across all metrics.
Frontier Airlines
Water Safety Score: 4.80 / Grade A
Aircraft Fleet Size: 171
Total ADWR Violations (Oct 2022-Sept 2025): 1
Avg # of ADWR Violations per Aircraft: 0.01
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 2
Total Coliform Positive Rate: 1.37%
Indicator Positive Rate: 1.05%
Public Notices per 100 Aircraft: 0.58
Comments: Frontier shows very low violations per aircraft and no Maximum Contaminant Level violations for E. coli.
Alaska Airlines
Water Safety Score: 3.85 / Grade B
Aircraft Fleet Size: 288
Total ADWR Violations (Oct 2022-Sept 2025): 8
Avg # of ADWR Violations per Aircraft: 0.03
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 0
Total Coliform Positive Rate: 0.88%
Indicator Positive Rate: 0.88%
Public Notices per 100 Aircraft: 2.08
Penalty Applied: Yes (alternative not clearly provided on at least one public notice)
Comments: Alaska shows no Maximum Contaminant Level violations for E. coli and a low indicator-positive rate, with one public notice response penalty reducing the overall score.
Allegiant Air
Water Safety Score: 3.65 / Grade B
Aircraft Fleet Size: 141
Total ADWR Violations (Oct 2022-Sept 2025): 9
Avg # of ADWR Violations per Aircraft: 0.06
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 4
Total Coliform Positive Rate: 1.31%
Indicator Positive Rate: 0.56%
Public Notices per 100 Aircraft: 1.42
Maximum Contaminant Level Violations for E. coli: 1
Comments: Allegiant has one Maximum Contaminant Level violation for E. coli, which is treated as a serious signal in the scoring model.
Southwest Airlines
Water Safety Score: 3.30 / Grade C
Aircraft Fleet Size: 914
Total ADWR Violations (Oct 2022-Sept 2025): 30
Avg # of ADWR Violations per Aircraft: 0.03
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 6
Total Coliform Positive Rate: 1.18%
Indicator Positive Rate: 1.06%
Public Notices per 100 Aircraft: 1.31
Maximum Contaminant Level Violations for E. coli: 5
Comments: Southwest shows multiple Maximum Contaminant Level violations for E. coli, a high-severity driver in the score.
Hawaiian Airlines
Water Safety Score: 3.15 / Grade C
Aircraft Fleet Size: 65
Total ADWR Violations (Oct 2022-Sept 2025): 48
Avg # of ADWR Violations per Aircraft: 0.74
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 0
Total Coliform Positive Rate: 4.31%
Indicator Positive Rate: 4.31%
Public Notices per 100 Aircraft: 10.77
Comments: Hawaiian shows high violations per aircraft and an elevated indicator-positive rate.
United Airlines
Water Safety Score: 2.70 / Grade C
Aircraft Fleet Size: 1,063
Total ADWR Violations (Oct 2022-Sept 2025): 105
Avg # of ADWR Violations per Aircraft: 0.10
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 7
Total Coliform Positive Rate: 2.38%
Indicator Positive Rate: 2.21%
Public Notices per 100 Aircraft: 0.00
Maximum Contaminant Level Violations for E. coli: 6
Comments: United shows multiple Maximum Contaminant Level violations for E. coli and an indicator-positive rate above the major-airline group average.
Spirit Airlines
Water Safety Score: 2.05 / Grade D
Aircraft Fleet Size: 248
Total ADWR Violations (Oct 2022-Sept 2025): 37
Avg # of ADWR Violations per Aircraft: 0.15
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 1
Total Coliform Positive Rate: 4.75%
Indicator Positive Rate: 4.67%
Public Notices per 100 Aircraft: 20.97
Maximum Contaminant Level Violations for E. coli: 1
Comments: Spirit shows an elevated indicator-positive rate and very high public notices per 100 aircraft.
JetBlue Airways
Water Safety Score: 1.80 / Grade D
Aircraft Fleet Size: 336
Total ADWR Violations (Oct 2022-Sept 2025): 220
Avg # of ADWR Violations per Aircraft: 0.65
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 6
Total Coliform Positive Rate: 5.67%
Indicator Positive Rate: 5.36%
Public Notices per 100 Aircraft: 8.63
Maximum Contaminant Level Violations for E. coli: 2
Comments: JetBlue shows a high violations-per-aircraft burden and an elevated indicator-positive rate.
American Airlines
Water Safety Score: 1.75 / Grade D
Aircraft Fleet Size: 995
Total ADWR Violations (Oct 2022-Sept 2025): 23
Avg # of ADWR Violations per Aircraft: 0.02
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 3
Total Coliform Positive Rate: 1.93%
Indicator Positive Rate: 1.86%
Public Notices per 100 Aircraft: 2.31
Maximum Contaminant Level Violations for E. coli: 3
Penalties Applied: Yes (alternative not clearly provided AND water system not clearly turned off on at least one public notice)
Comments: American's score is materially lowered by public notice response penalties and Maximum Contaminant Level violations for E. coli. American had the worst score among major airlines.
Regional Airlines
GoJet Airlines
Water Safety Score: 3.85 / Grade B
Aircraft Fleet Size: 58
Total ADWR Violations (Oct 2022-Sept 2025): 0
Avg # of ADWR Violations per Aircraft: 0.00
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 0
Total Coliform Positive Rate: 4.20%
Indicator Positive Rate: 4.20%
Public Notices per 100 Aircraft: 5.17
Comments: GoJet had zero ADWR violations and zero Maximum Contaminant Level violations for E. coli, receiving the highest score among regional carriers.
Piedmont Airlines (operates as American Eagle, owned by American Airlines)
Water Safety Score: 3.05 / Grade C
Aircraft Fleet Size: 81
Total ADWR Violations (Oct 2022-Sept 2025): 11
Avg # of ADWR Violations per Aircraft: 0.14
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 0
Total Coliform Positive Rate: 11.52%
Indicator Positive Rate: 11.52%
Public Notices per 100 Aircraft: 9.88
Comments: Despite having no E. coli violations, Piedmont shows an elevated indicator-positive rate.
Sun Country Airlines
Water Safety Score: 3.00 / Grade C
Aircraft Fleet Size: 46
Total ADWR Violations (Oct 2022-Sept 2025): 78
Avg # of ADWR Violations per Aircraft: 1.70
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 0
Total Coliform Positive Rate: 1.64%
Indicator Positive Rate: 1.64%
Public Notices per 100 Aircraft: 26.09
Comments: Sun Country has a very high violations-per-aircraft rate and elevated public notices.
Endeavor Air (operates as Delta Connection, owned by Delta Air Lines)
Water Safety Score: 2.95 / Grade C
Aircraft Fleet Size: 169
Total ADWR Violations (Oct 2022-Sept 2025): 10
Avg # of ADWR Violations per Aircraft: 0.06
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 1
Total Coliform Positive Rate: 1.65%
Indicator Positive Rate: 1.50%
Public Notices per 100 Aircraft: 6.51
Maximum Contaminant Level Violations for E. coli: 1
SkyWest Airlines
Water Safety Score: 2.40 / Grade D
Aircraft Fleet Size: 575
Total ADWR Violations (Oct 2022-Sept 2025): 1
Avg # of ADWR Violations per Aircraft: 0.00
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 3
Total Coliform Positive Rate: 2.06%
Indicator Positive Rate: 1.97%
Public Notices per 100 Aircraft: 10.96
Maximum Contaminant Level Violations for E. coli: 1
Penalty Applied: Yes (alternative not clearly provided on at least one public notice)
Envoy Air (operates as American Eagle, owned by American Airlines)
Water Safety Score: 2.30 / Grade D
Aircraft Fleet Size: 204
Total ADWR Violations (Oct 2022-Sept 2025): 24
Avg # of ADWR Violations per Aircraft: 0.12
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 4
Total Coliform Positive Rate: 1.62%
Indicator Positive Rate: 1.08%
Public Notices per 100 Aircraft: 6.37
Maximum Contaminant Level Violations for E. coli: 4
PSA Airlines (operates as American Eagle, owned by American Airlines)
Water Safety Score: 2.25 / Grade D
Aircraft Fleet Size: 121
Total ADWR Violations (Oct 2022-Sept 2025): 22
Avg # of ADWR Violations per Aircraft: 0.18
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 2
Total Coliform Positive Rate: 6.76%
Indicator Positive Rate: 6.35%
Public Notices per 100 Aircraft: 8.26
Maximum Contaminant Level Violations for E. coli: 1
Air Wisconsin Airlines (operates as United Express)
Water Safety Score: 2.15 / Grade D
Aircraft Fleet Size: 52
Total ADWR Violations (Oct 2022-Sept 2025): 28
Avg # of ADWR Violations per Aircraft: 0.54
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 1
Total Coliform Positive Rate: 3.91%
Indicator Positive Rate: 3.52%
Public Notices per 100 Aircraft: 23.08
Maximum Contaminant Level Violations for E. coli: 1
Republic Airways (operates as United Express, Delta Connection, American Eagle)
Water Safety Score: 2.05 / Grade D
Aircraft Fleet Size: 252
Total ADWR Violations (Oct 2022-Sept 2025): 201
Avg # of ADWR Violations per Aircraft: 0.80
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 2
Total Coliform Positive Rate: 2.44%
Indicator Positive Rate: 2.30%
Public Notices per 100 Aircraft: 5.16
Maximum Contaminant Level Violations for E. coli: 2
CommuteAir
Water Safety Score: 1.60 / Grade D
Aircraft Fleet Size: 65
Total ADWR Violations (Oct 2022-Sept 2025): 19
Avg # of ADWR Violations per Aircraft: 0.29
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 6
Total Coliform Positive Rate: 33.33%
Indicator Positive Rate: 32.21%
Public Notices per 100 Aircraft: 84.62
Maximum Contaminant Level Violations for E. coli: 2
Comments: Alarming. CommuteAir shows an exceptionally high total coliform positive rate (33.33%) and very high public notices per aircraft.
Mesa Airlines
Water Safety Score: 1.35 / Grade F
Aircraft Fleet Size: 101
Total ADWR Violations (Oct 2022-Sept 2025): 47
Avg # of ADWR Violations per Aircraft: 0.47
Total Water Samples Testing Positive For E. Coli (Oct 2022-Sept 2025): 2
Total Coliform Positive Rate: 6.10%
Indicator Positive Rate: 5.49%
Public Notices per 100 Aircraft: 18.81
Maximum Contaminant Level Violations for E. coli: 2
Comments: Mesa received the only failing grade among rated airlines, with poor performance across multiple metrics.
About the Study
The 2026 Airline Water Study was conducted by the Center for Food as Medicine and Longevity using Aircraft Drinking Water Rule compliance, operational, sampling, and public notice records from the United States Environmental Protection Agency for the period October 1, 2022 through September 30, 2025. The study analyzed 35,674 total sample locations tested across 21 airlines.
