SMS Quick Takes: 14 CFR § 5.57: Notifying Interfacing Persons
In our previous post, we introduced Ridgeline Air’s Safety Risk Management (SRM) process. There we noted a hazard that stood out, unrelated to terrain and weather, was an unfamiliar contract fueling provider with unknown quality‑control processes. It was prudent to flag that hazard because it relates directly to Title 14, Code of Federal Regulations (14 CFR) part 5, § 5.57: the obligation to notify interfacing persons when you identify a hazard in your operating environment.
What §5.57 Actually Says
The regulatory text is concise:
If a person required to have an SMS under this part identifies a hazard in the operating environment, the person must provide notice of the hazard to any interfacing person that, to the best of the person’s knowledge, could address the hazard or mitigate the risk.
Part 5 defines “interfacing persons” as those who contribute to the safety of the certificate or Letter of Authorization‑holder’s aviation‑related products and services. This broad definition can include fixed‑base operators (FBO), contract maintenance providers, ground handlers, fueling vendors, and other certificate holders whose work intersects with your operation. You must also keep records of these mandatory notices for a minimum of 24 consecutive calendar months under § 5.97(d).
Why This Requirement Exists: The Punta Gorda Incident
On May 9, 2019, two Cessna Citation 550s, operated by Air Ambulance operator Air Trek, Inc., departed Punta Gorda Airport (KPGD) and flew to Naples, Florida, where passengers connected to Niagara Falls and Chicago. Both aircraft had been fueled at Punta Gorda with jet fuel contaminated by diesel exhaust fluid (DEF), which had been inadvertently mixed with fuel system icing inhibitor (FSII) by an FBO line service employee. It went undetected during preflight fuel checks because DEF is colorless and odorless. When it mixes with jet fuel, it forms deposits that can clog fuel filters and fuel‑system components (NTSB ERA19IA178).
Because of the contamination, one Citation lost its left engine while it was en route at FL350 and declared an emergency. As the flight descended it lost the right engine and dead‑sticked to a landing at Savannah Hilton Head International Airport (KSAV). The other aircraft lost an engine and diverted to Louisville International Airport (KSDF). In all, 13 occupants escaped without injury—a testament to the professionalism and airmanship of the Air Trek flightcrews, who were later recognized by the National Business Aviation Association (NBAA) for their exceptional handling of the emergency.
The Punta Gorda FBO had fueled seven aircraft that day from the same contaminated truck. The National Transportation Safety Board (NTSB) subsequently issued Safety Alert SA–079, Fuel Providers: Prevent DEF Jet Fuel Contamination, in July 2019, and the FAA issued Safety Alert for Operators (SAFO) 18015R1, Jet Fuel Contaminated with Diesel Exhaust Fluid (DEF). The incident was a direct illustration of what happens when a hazard at the interface between an operator and its fuel provider goes unaddressed (Fuel Contamination Downs Two Citations). Section 5.57 exists, in part, because of events like this one.
Bringing It Back to Ridgeline Air
In our SRM scenario from the previous blog post, Ridgeline Air’s safety manager identified the contract fueling provider at the new destination as a hazard source because Ridgeline was unfamiliar with this vendor and its quality control process. The safety team developed a risk control: obtain fuel‑quality documentation from the provider and establish a formal supplier evaluation process.
But what if, during that evaluation, Ridgeline Air discovered a deficiency? Perhaps there are improper DEF storage practices near the fueling area, or FSII containers are inadequately labeled. Under § 5.57, Ridgeline Air would be obligated to notify the FBO of the identified hazard, because the FBO clearly contributes to the safety of Ridgeline Air’s operations and could act to mitigate the risk.
Notably, Advisory Circular (AC) 120-92D § 3.4.7.3 clarifies the § 5.57 notification obligation applies regardless of whether the interfacing organization has its own SMS—the requirement exists to ensure all potentially affected entities are made aware of hazards so they can analyze the risks and take appropriate action. The FBO does not need to have an SMS for Ridgeline Air’s notification obligation to apply.
This is where § 5.57 closes a loop SRM alone cannot: Ridgeline Air cannot control the FBO’s internal processes, but under part 5, it must communicate the hazard to those who can.
Meeting § 5.57 in Practice
The FAA has provided practical guidance in AC 120–92D § 3.4.7.4.3 on how operators can satisfy the § 5.57 requirement using a three‑step process:
Confirm an external organization (interfacing person) could address the hazard or mitigate its risk.
Confirm the interfacing person directly contributes to the safety of the products or services you provide.
Provide the hazard notification. (Note: per AC 120–92D, proprietary or confidential information may be removed and a non‑disclosure agreement used if the notification cannot be provided without disclosing such information.)
One important boundary: AC 120–92D § 3.4.7.4.1 clarifies § 5.57 applies only to identified hazards and not general operational concerns or commercial disputes between companies: the intent is timely sharing of safety information, nothing more.
For a small 14 CFR part 135 operators like Ridgeline Air, where the safety manager likely wears several hats, this does not need to be a formal legal document—a clear, professional email is sufficient. Here is what that might look like in the following sample email:
Subject: Safety Hazard Notification—Fuel Quality Control Practices
Dear [FBO Operations Manager],
Ridgeline Air is writing to notify you of a safety concern identified during our supplier evaluation process, in connection with our planned operations at [Destination Airport].
During our evaluation, we were unable to confirm the following fuel quality control practices at your facility:
Segregated storage and clear labeling of FSII and DEF containers,
Documented procedures for verifying correct additive use before fuel‑truck servicing, and
Personnel training records related to fuel contamination prevention.
We bring this to your attention because fuel quality directly contributes to the safety of our operations, and we believe your team is best positioned to address these practices. We are happy to share FAA SAFO 18015R1 if that would be helpful, and we would welcome a response describing any corrective actions taken or planned.
This notification is provided in accordance with our SMS obligations under 14 CFR part 5, § 5.57.
Respectfully, [Safety Manager Name], Ridgeline Air
The tone matters here: this is a safety communication between two parties with a shared interest in safe operations, not a complaint letter. Keeping it professional and collaborative preserves the working relationship while meeting the regulatory obligation.
Equally as important as sending the notification is documenting it. For a small operator, a simple entry in the hazard registry is sufficient. It should capture, at minimum—
Hazard Registry Entry
RA–HZ–2025–004
A copy of the email itself should be retained alongside the registry entry: AC 120–92D § 3.4.7.4.2 specifically recommends even single‑individual organizations retain hazard notification outputs for no less than 24 calendar months (consistent with § 5.97(d)). For a small part 135 operator, the email plus the registry entry together satisfy both requirements. If the FBO never responds, that open status becomes a data point for Safety Assurance monitoring under § 5.73 and may warrant a followup SRM review before Ridgeline Air begins revenue operations at that destination.
The Bigger Picture
Section 5.57 reflects a fundamental SMS principle: safety does not stop at your certificate boundary. Your operation touches vendors, contractors, ground handlers, and other certificate holders every day, and hazards originating or residing in those interfaces are still your hazards to identify and communicate.
The Punta Gorda incident is a stark reminder of what is at stake when that communication does not happen. Although two flightcrews brought two aircraft home safely, the deposits forming in those fuel systems were invisible to everyone until the engines started unwinding at altitude. Section 5.57 is not a bureaucratic notification requirement, but the regulatory recognition that safety information, shared across organizational boundaries, is what keeps those engines running.
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