You are a dual-licensed EASA/FAA mechanic working the line in London. A Boeing 787 rolls into your gate with an engine snag. The aircraft is designed in the United States (FAA), operated by a Qatari airline (QCAA), and is sitting on British tarmac (UK CAA).
When you pull out the manuals to defer the defect, whose rules are you actually following?
Aviation is a borderless industry governed by strictly bordered laws. If you apply an FAA standard to a QCAA-registered aircraft simply because it is a Boeing, you have performed an illegal repair and invalidated the aircraft’s Certificate of Airworthiness (C of A).
For line mechanics and AME students, knowing how to turn a wrench is only half the job. You must understand the chain of command above the manual. Here is the hangar-floor guide to the global regulatory hierarchy, from the UN down to your local ramp.
Level 1: The Global Architect (ICAO)
Before a single law is written by the FAA or EASA, the baseline is established by the International Civil Aviation Organization (ICAO).
ICAO is not a police force. It is a specialized agency of the United Nations headquartered in Montreal, born from the Chicago Convention of 1944. ICAO does not issue licenses, write Airworthiness Directives, or fine airlines. Instead, it writes SARPs (Standards and Recommended Practices).
- The Mechanism: ICAO publishes 19 Annexes. For mechanics, the bibles are Annex 1 (Personnel Licensing) and Annex 8 (Airworthiness of Aircraft).
- The Tarmac Reality: ICAO dictates the minimum global safety standards. When ICAO dictates in Annex 8 that an aircraft must have a maintenance manual, it is up to the individual countries to write the actual laws enforcing that rule.
Level 2: State of Design & Manufacture (FAA / EASA)
When ICAO sets the standard, national heavyweights like the FAA (United States) and EASA (European Union) translate those SARPs into hard, enforceable laws (like 14 CFR and EASA Parts).
Because Airbus and Boeing dominate the global market, EASA and the FAA act as the State of Design and State of Manufacture for the vast majority of commercial aircraft.
- The Type Certificate (TC): When Boeing builds the 737 MAX, the FAA (as the State of Design) approves its blueprint and issues the Type Certificate.
- The Master Data: The State of Design approves the absolute baseline airworthiness data: the Master Minimum Equipment List (MMEL), the Aircraft Maintenance Manual (AMM), and the Structural Repair Manual (SRM).
- Airworthiness Directives (ADs): If a design flaw is found on an A320, EASA (the State of Design) issues the AD. Global operators of the A320 must comply, but they do so under the enforcement of their local authority.
Level 3: The Ultimate Boss — State of Registry (Local NAAs)
This is the most critical concept for a line mechanic to grasp: The law that governs the aircraft is the law of the country where the aircraft is registered.
Under Article 17 of the Chicago Convention, aircraft have the nationality of the State in which they are registered. Your local National Aviation Authority (NAA)—whether it is the UK CAA, the Indian DGCA, the Australian CASA, or the UAE GCAA—is the State of Registry.
| Authority Level | Their Role on the Hangar Floor |
| State of Design (e.g., FAA for Boeing) | Writes the MMEL, issues the baseline ADs, approves the SRM. |
| State of Registry (e.g., DGCA for an Indian airline) | Issues the aircraft’s C of A, approves the Operator MEL, issues the mechanic’s license, and enforces the maintenance schedule. |
THE GOLDEN RULE: The State of Registry can adopt the State of Design’s rules, or they can make them stricter. They can NEVER make them less restrictive than the ICAO baseline. If the FAA MMEL says a part can be deferred for 10 days, but the local NAA (State of Registry) says 3 days, the local NAA wins.
Tarmac Scenario: The Overlapping Jurisdiction
The Snag: You are a line mechanic in Singapore. A Boeing 777-300ER lands with a damaged thrust reverser translating cowl. The aircraft is built by Boeing (FAA State of Design) but is registered in Australia and operated by an Australian airline (CASA State of Registry).
Diagnostic & Regulatory Logic:
- The Manuals: You pull the Boeing AMM to find the lockout procedure. Because Boeing wrote the manual, it is FAA-approved data.
- The Deferral: You cannot dispatch using the Boeing MMEL. You must use the airline’s specific Operator MEL, which has been legally approved by Australian CASA.
- The Conflict: The Boeing SRM (FAA approved) says a specific temporary repair requires a form to be filed with the FAA. However, Australian law dictates that major repairs on their registry must be approved by a CASA-authorized Part 21M engineer.
- Action: You apply the State of Registry rule. You follow the Boeing AMM for the physical wrench-turning, but the legal approval, defect deferral time limits, and the final Certificate of Release to Service (CRS) statement in the logbook must strictly adhere to the Australian CASA regulations.
WARNING: UNAUTHORIZED DATA. Never assume that an FAA-approved repair scheme (like an 8110-3 DER approval) is automatically valid on a foreign-registered aircraft. The State of Registry’s NAA must legally accept that foreign engineering data before you can sign the tech log.
Connecting the Global Network: Bilateral Agreements
If every local NAA had to independently re-certify every Boeing or Airbus that entered their country, global aviation would gridlock.
To solve this, countries sign Bilateral Aviation Safety Agreements (BASA). As we covered in the MAG guide, a BASA allows the local NAA to legally say, “We trust the FAA’s engineering data, and we will automatically accept it for aircraft on our registry.”
When you are clearing a snag, the hierarchy is always working in the background. ICAO built the foundation, the FAA/EASA built the manuals, but the local NAA on the tail of the aircraft is the ultimate authority that owns your signature. Read the tail number, know the registry, and apply the right law.
