An Aircraft Certification Office Is Your FAA's Local Authority for Airplane Safety

An Aircraft Certification Office (ACO) is a regional branch of the Federal Aviation Administration (FAA) that approves aircraft designs, oversees manufacturing, and certifies that planes are safe to fly. If you own, build, or maintain an aircraft, or if you work in aviation manufacturing, an ACO is the government body you will deal with directly. They do not issue pilot licenses — that is a different FAA office — but they do decide whether your aircraft can legally leave the ground.

The FAA divides the country into regions, and each region has one or more ACOs. For example, the Seattle ACO covers Washington and Oregon; the Atlanta ACO covers Georgia, Florida, and parts of nearby states. When you need certification for a new aircraft design, a homebuilt plane, or major repairs, you contact the ACO that covers your location, not a central FAA office.

Key Takeaways

  • Aircraft Certification Offices are regional FAA branches that approve aircraft designs and issue airworthiness certificates before planes can fly legally.
  • You contact your local ACO based on where the aircraft is built or registered, not a national office.
  • ACOs handle type certification (new designs), production certification (manufacturing), and special certificates for experimental or amateur-built aircraft.
  • The certification process can take months to years depending on whether the aircraft is a new design, a production model, or a one-off build.
  • ACOs also conduct inspections and oversee compliance with airworthiness standards throughout an aircraft's life.

What Aircraft Certification Offices Actually Approve

An ACO handles three main types of certification. Type certification means the FAA has reviewed a new aircraft design — the blueprints, materials, systems, and performance data — and determined it is safe. This is what manufacturers need before they can build and sell a model. A single type certificate can cover thousands of aircraft of the same design.

Production certification means the FAA has inspected the factory and approved the manufacturing process. Even if a design is type-certified, the factory must prove it can build each plane to that standard. The ACO sends inspectors to watch production, review quality control, and verify that parts meet specifications.

Airworthiness certificates are issued for individual aircraft. Before any plane — whether brand new, used, or homebuilt — can fly, it must have an airworthiness certificate showing it meets FAA standards. The ACO issues this certificate after an inspection confirms the aircraft is in safe condition and properly maintained.

How to Find Your Local Aircraft Certification Office

The FAA website lists all ACOs by region. You can search by state or by the city where your aircraft is located or will be built. Each ACO has a phone number, mailing address, and email contact for different departments — design, manufacturing, airworthiness, and special certificates.

If you are unsure which office covers your area, call the main FAA Flight Standards District Office (FSDO) for your state. The FSDO and ACO work together, and the FSDO staff can direct you to the right ACO. You can also contact the FAA's general aviation hotline, which can route you to the correct office based on your project type and location.

The Certification Process Takes Time and Requires Documentation

The timeline depends on what you are certifying. A new aircraft type can take two to five years or longer because the FAA must review engineering data, conduct flight tests, and verify that the design meets hundreds of safety standards. A production certificate for an existing type usually takes several months. An airworthiness certificate for a used aircraft or homebuilt plane can take weeks to a few months, depending on the aircraft's condition and history.

You will need to provide detailed documentation: engineering drawings, materials specifications, maintenance records, test data, and proof that the aircraft meets applicable airworthiness standards. For homebuilt aircraft, you must show that construction followed approved plans or that you have FAA permission to deviate from them. For used aircraft, you need maintenance logs and evidence of any major repairs or modifications.

The ACO assigns an inspector or certification specialist to your project. This person becomes your main contact and guides you through what documents are needed, what inspections will happen, and what standards explore to your specific aircraft.

Special Certificates for Experimental and Amateur-Built Aircraft

Not every aircraft needs full type and production certification. If you are building an aircraft at home or testing a new design, you can request a special airworthiness certificate in the experimental category. This allows you to fly the aircraft for specific purposes — research, crew training, or personal use — without going through the full certification process.

An amateur-built aircraft (also called a homebuilt) follows a different path. You must show that you did the majority of the construction yourself, and the ACO will issue an experimental certificate once the aircraft is complete and passes an inspection. This certificate lets you fly the plane, but it comes with restrictions: you cannot carry paying passengers, and you must follow specific operating limits.

The ACO also issues special certificates for light-sport aircraft, which are simpler designs that meet a different set of standards than conventional aircraft. These certificates have their own requirements and timelines.

What Happens After Certification

Certification is not a one-time event. Once an aircraft has an airworthiness certificate, it must be maintained according to FAA rules. The ACO does not conduct routine maintenance inspections — that is the owner's or operator's responsibility — but the ACO can investigate if there are safety concerns or if an aircraft has been involved in an accident.

If you make major modifications to a certified aircraft, you may need to contact the ACO again. Adding new equipment, changing the engine, or altering the structure can require a new inspection or supplemental certification. The ACO helps determine whether your modification affects airworthiness and what additional steps are needed.

The ACO also oversees compliance with airworthiness directives (ADs), which are FAA orders requiring specific repairs or inspections on certain aircraft models. If an ACO discovers a safety issue affecting multiple aircraft of the same type, it can issue an AD, and the ACO tracks whether owners are complying.

Why the ACO Matters to Aircraft Owners and Builders

The ACO is the bridge between you and federal safety standards. They translate complex regulations into practical steps for your specific aircraft. If you are unsure whether your modification is legal, whether your aircraft meets current standards, or what paperwork you need, the ACO can answer those questions before you invest time and money in the wrong direction.

Building or modifying an aircraft without involving the ACO early can lead to costly mistakes. An aircraft that does not meet standards cannot be legally flown, and reworking it after the fact is more expensive than getting guidance upfront. The ACO's role is to help you understand the rules and build or maintain an aircraft that is both legal and safe.

Frequently Asked Questions

Do I need to contact an Aircraft Certification Office if I buy a used airplane?

Not usually. If the aircraft already has a valid airworthiness certificate, you can transfer ownership without ACO involvement. However, if the aircraft has been damaged, heavily modified, or has been out of service for a long time, you may need an ACO inspection before you can fly it again.

What is the difference between an Aircraft Certification Office and a Flight Standards District Office?

An ACO focuses on aircraft design, manufacturing, and airworthiness certification. An FSDO handles pilot licensing, flight training, and operational rules for flying. They work together, but they handle different aspects of aviation safety.

Can I fly an experimental aircraft on public roads or over populated areas?

No. An experimental airworthiness certificate comes with operating restrictions. You typically cannot fly over populated areas, and you must stay within a specific flight test area. The ACO specifies these limits when it issues your certificate.

How much does it cost to get an aircraft certified?

The ACO itself does not charge a fee for certification, but you pay for inspections, engineering consultants, and any modifications needed to meet standards. Costs vary widely depending on the aircraft type and complexity. A homebuilt certification might cost a few thousand dollars; a new aircraft type can cost hundreds of thousands.

What if my aircraft fails inspection?

The ACO will tell you what does not meet standards and what you need to fix. You then make the repairs or modifications and request a follow-up inspection. The process repeats until the aircraft passes. There is no limit to how many times you can resubmit for inspection.