Aircraft placard and marking requirements are not found in AC 20-152A. That advisory circular covers development assurance for airborne electronic hardware, such as ASICs and field-programmable gate arrays, and has nothing to do with the visual markings on an aircraft.1Federal Aviation Administration. AC 20-152A Development Assurance for Electronic Hardware The rules you want are in Title 14 of the Code of Federal Regulations: Part 45 for the N-number, the Subpart G of Parts 23, 25, 27, and 29 for operational and safety placards, and 14 CFR 91.9, which makes flying without the required markings a violation.
Where the Rules Actually Live
Placard and marking obligations sit in three places in the CFR, and they work together.
- 14 CFR Part 45, Subpart C sets the nationality and registration marks: size, format, placement, and permanence of the N-number.
- 14 CFR Parts 23, 25, 27, and 29, each in Subpart G, contain the airworthiness standards for markings and placards specific to that aircraft category: cockpit instruments, operational limits, fuel and oil markings, cargo placards, and safety equipment labels.
- 14 CFR 91.9 prohibits operating a civil aircraft without complying with the operating limitations in its approved flight manual, markings, and placards.
Part 45 tells you how to display identification. The airworthiness parts tell you what operational and safety information must be placarded. Part 91 turns any missing or illegible required marking into an operating violation.
Nationality and Registration Marks
Every U.S.-registered aircraft displays the Roman capital letter “N” followed by its registration number. The marks must be painted on or affixed with similar permanence, contrast with the background, carry no ornamentation, and stay legible. Readily removable materials are allowed only in narrow situations, such as aircraft awaiting immediate delivery to a foreign buyer or bearing a temporary number.2eCFR. 14 CFR Part 45 Subpart C – Nationality and Registration Marks
Placement
Fixed-wing aircraft carry their marks either on the vertical tail surfaces or on both sides of the fuselage between the trailing edge of the wing and the leading edge of the horizontal stabilizer. Either way, they run horizontally and appear on both sides.3eCFR. 14 CFR 45.25 – Location of Marks on Fixed-Wing Aircraft Rotorcraft display the marks horizontally on both surfaces of the cabin, fuselage, boom, or tail.
Size and Formatting
Most fixed-wing aircraft and all rotorcraft use characters at least 12 inches high. Gliders and certain experimental or amateur-built aircraft with a maximum cruising speed of 180 knots CAS or less may use 3-inch marks. Airships, balloons, powered parachutes, and weight-shift-control aircraft also use a 3-inch minimum.4eCFR. 14 CFR 45.29 – Size of Marks
The character geometry is specific:
- Width is two-thirds of the height, except the numeral “1” (one-sixth) and the letters “M” and “W” (may be as wide as they are tall).
- Stroke thickness is one-sixth of the character height, formed by solid lines.
- Spacing between characters is at least one-fourth of a character width.
- Marks on both sides of a fixed-wing aircraft must match in height, width, thickness, and spacing.
If neither approved surface is large enough for full-size marks, the operator displays them as large as practicable on the larger surface.
Cockpit and Interior Placards
Each aircraft category’s Subpart G lists the specific markings and placards required inside. For transport category airplanes under Part 25, the aircraft must contain all specified markings and placards, plus any additional information needed for safe operation if the design or handling has unusual characteristics. Every marking must be conspicuous and cannot be easily erased, disfigured, or obscured.5eCFR. 14 CFR 25.1541 – General
Cockpit markings typically cover instrument range arcs and operational limit indicators. Color-coded bands on the airspeed indicator and engine gauges let pilots read at a glance whether a parameter is inside safe limits. The exact instruments requiring markings vary by category, but the applicable Subpart G lays them out.
Cargo and Baggage Compartments
Each baggage and cargo compartment carries a placard stating any weight or content limitations tied to the aircraft’s loading requirements. Underseat compartments designed for carry-on articles weighing no more than 20 pounds are the practical exception and do not need a loading limitation placard.6eCFR. 14 CFR 25.1557 – Miscellaneous Markings and Placards
No-Smoking and Seatbelt Signs
Large passenger-carrying aircraft need illuminated signs that tell passengers when smoking is prohibited and when seatbelts must be fastened. The seatbelt signs stay crew-controllable and must be illuminated during surface movement, takeoff, landing, and whenever the pilot in command decides they are needed.7eCFR. 14 CFR 91.517 – Passenger Information Requirements Under Part 121, the no-smoking signs remain lit for the entire flight, or alternatively, placards meeting the legibility standards of 14 CFR 25.1541 are posted throughout the flight.8eCFR. 14 CFR 121.317 – Passenger Information Requirements, Smoking Prohibitions Smaller aircraft without installed sign systems satisfy the requirement through an oral briefing from the pilot in command.
Emergency Exit Markings
Transport category exit markings are among the most detailed rules in the CFR. Every passenger emergency exit, its means of access, and its means of opening must be conspicuously marked, and each exit’s identity and location must be recognizable from a distance equal to the width of the cabin.9eCFR. 14 CFR 25.811 – Emergency Exit Marking
Interior signage includes locator signs above the aisle near each exit, marking signs next to each exit, and signs on any bulkhead that blocks the view of exits behind it. Exits that use rotary-handle locking mechanisms carry a red arrow showing the direction of handle travel, with the word “OPEN” in red letters at least 1 inch high near the arrowhead. On the outside, each emergency exit that must open from outside is outlined with a 2-inch colored band, and the band and surrounding paint must give enough contrast against the fuselage to be readily distinguishable.
Fuel and Oil Filler Markings
Every fuel filler opening carries a marking at or near the filler cover. For transport category airplanes, the marking includes the word “fuel” plus additional information depending on the engine: reciprocating-engine airplanes show the minimum fuel grade, and turbine-powered airplanes show the permissible fuel designations. Pressure fueling systems also show the maximum permissible fueling and defueling pressures.6eCFR. 14 CFR 25.1557 – Miscellaneous Markings and Placards
Oil filler openings are marked at or near the filler cover with the word “oil.” Part 23 imposes parallel rules for normal and utility category airplanes: reciprocating aircraft show “Avgas” with the minimum grade, and turbine aircraft show “Jet Fuel” with permissible designations.10GovInfo. 14 CFR 23.1557 – Miscellaneous Markings and Placards Misfueling incidents have caused fatal accidents, and correct filler markings are the front line against them.
The Operating Rule That Ties It Together
The enforcement mechanism for every marking rule above is 14 CFR 91.9. No person may operate a civil aircraft without complying with the operating limitations specified in its approved flight manual, markings, and placards.11eCFR. 14 CFR 91.9 – Civil Aircraft Flight Manual, Marking, and Placard Requirements A required placard that is missing, faded, peeled, or illegible can make the aircraft unairworthy until it is corrected.
Aircraft that require an approved flight manual must carry a current copy on board. Aircraft that do not require a formal flight manual must carry approved manual material, markings, placards, or some combination.11eCFR. 14 CFR 91.9 – Civil Aircraft Flight Manual, Marking, and Placard Requirements Ramp checks and annual inspections are where placard deficiencies typically surface.
Penalties for Non-Compliance
The FAA can take enforcement action against operators who fly with missing or non-compliant markings. As of 2025, the civil penalty for a violation by an individual airman can reach $1,875 per violation. Individuals or small business concerns not serving as airmen face penalties up to $17,062 per violation. Other entities can be penalized up to $75,000 per violation, with amounts adjusted periodically for inflation.12Federal Register. Revisions to Civil Penalty Amounts, 2025
Beyond fines, the FAA can pursue certificate action against pilots and mechanics, which may lead to suspension or revocation. In practice, a single missing placard found during a ramp check is more often handled with a counseling letter or a requirement to correct the deficiency before further flight. Repeated violations, or markings so deficient that safety is compromised, escalate faster. Registration mark violations under Part 45 carry particular weight because the marks tie directly to aircraft identification for air traffic control and law enforcement.
Flammability Rules for Interior Placards and Decals
Interior cabin materials on transport category airplanes, including finishes and decorative surfaces, must meet the flammability test criteria in 14 CFR 25.853.13eCFR. 14 CFR 25.853 – Compartment Interiors The rule does not name placards or decals specifically, but the requirement applies to interior materials generally. Aircraft with 20 or more passenger seats face additional heat release and smoke testing on wall panels, partitions, galley structures, and large stowage compartments. Any decal affixed to those surfaces effectively becomes part of the interior material, so manufacturers and repair stations specify fire-resistant adhesives and substrates for interior decals to keep the certified fire performance intact.