What Is An MRO In Aviation?

‍Aviation has enough acronyms to fill the cargo hold of the An-225. MRO is just one of these acronyms, but what exactly is an MRO and what does it do?

In aviation, MRO stands for Maintenance, Repair and Overhaul. It is an aircraft maintenance facility that offers specialized engineering services for aircraft operators, including parts servicing, general maintenance and aircraft inspections among other things. There are around 350 MROs in the US.

I’ve been a corporate pilot for the last 15 years and have spent several of those years in charge of a flight department. This means I’ve come across MROs from every angle bar a mechanic, so I’m very experienced in what they are, and what they do.

‍What Is an MRO in Aviation?

The letters MRO are used as an acronym in many industries to mean Maintenance Repair and Overhaul.. In aviation, an MRO is a maintenance facility that performs the required maintenance and inspection.

The FAA requires a certified entity to perform all aircraft maintenance, inspection, repair, and overhaul. An MRO is among the qualifying entities that maintain, repair and overhaul aircraft, engines, and accessories.

Most MROs serve as FAA Certified Repair Stations and perform specific maintenance that adheres to the incredibly specific FAA Operation Specifications. The A&P license of each mechanic is the FAA-certified entity for general maintenance in some MROs.

Differences in Maintenance, Repair, and Overhaul

Maintenance includes the inspection and routine upkeep of aircraft items and the repair of discrepancies. Repair refers to returning an aircraft, accessory, or component to a serviceable condition.

An overhaul repairs and replaces aircraft accessories, components, or engines to the Original Equipment Manufacturer (OEM) standards. The FAA or manufacturer may require these items to be overhauled, depending on the rule of the FAA the aircraft is operating.

The Difference Between MRO and General Aircraft Maintenance

Depending on where you live, an MRO and general aircraft maintenance might be one in the same. This is particularly common in smaller and/or more rural areas.

Regardless, most of the time an MRO is a Certificate Repair Station (CRS). The difference between an MRO that uses an A&P certificate and a CRS is that the FAA has more oversight and control over the latter.

From a pilot or aircraft owner’s perspective, a CRS is going to be mildly more expensive - as they have stricter record keeping, more expensive equipment and tools and general training - but generally do a better job to a much higher standard.

What Are Aviation MRO Service Items?

Typically, MROs are associated with pilots’ dreaded A, B, C, and D checks as well as the similarly dreaded 60, 72, 96 and 120-month inspections, or more general heavy maintenance.

Other items an MRO might service include avionics, general repair and/or overhaul of major components and the landing gear, which all require the specialist tools an MRO has.

MRO Facilities

As a general rule, most MRO facilities are located in buildings (often hangars acting as workshops) at your local airport. Generally, the type and size of building an MRO will operate out of depends on the services it offers to guarantee safety and suitability.

MRO services, however, are not just limited to maintaining, repairing, and overhauling commercial airplanes. MROs can also offer their services for corporate jets, helicopters, cargo aircraft and other special-use aircraft.

How Does an Aviation MRO Work?

MRO involves activities that range from repairing components to maintenance activities to overhauling services. The activities performed at an MRO facility may include the following:

• Aircraft maintenance and inspection
• Aircraft overhauls and repairs
• Independent repair stations
• Fixed-base operators.
• Commercial airline hubs
• Defense MRO companies

Aircraft Maintenance and Inspection

Maintenance refers to work done to keep aircraft in optimal condition. It is usually preventative or planned maintenance or performed when any potential issue is discovered during an inspection.

Maintenance and repair are different. Components that require maintenance are not necessarily not working or completely broken. Aircraft maintenance includes lubricating fittings, the nose gear retract actuator or verifying the emergency lights work, and the parking brake pressure accumulation.

Aircraft Overhauls and Repair

An aircraft overhaul requires part-by-part disassembly. Every part is meticulously inspected for potential issues and its suitability for further operation is decided on a part-by-part basis.

Mechanics look for unusual wear and/or hidden damage. Any component not fit for its purpose is replaced according to specifications and standards using brand new parts from the factory.

Repairs may be necessary after the aircraft has been inspected or had maintenance. The most common components that require repair are things like broken windows (both the glass and the plastic shutter inside the cabin), as well as structural issues such as dents.

More serious repairs such as faulty control panels or surfaces are generally much rarer, though are more time consuming.

Independent Repair Stations

Independent repair stations are among the simplest MRO business models. They are organizations specializing in specific repair areas, often common things like electrical systems or airframes. The repair stations can sometimes be just a branch of a bigger organization that owns a number of aircraft repair stations.

These ones in particular are generally more prominent than standard independent repair stations and can often be found at larger airports providing their services to small airlines/aircraft operators rather than the general public.

Fixed-Based Operators

Whilst two very different organizations, fixed base operators (FBOs) work closely with MROs. At airports with MROs, there are typically FBOs (and vice versa) meaning that many clients of FBOs also use the MRO and vice versa. This means that MROs and pilots often split the bill for costs like parking and fueling.

Commercial Airline Hubs

Most major airlines, such as British Airways, Qantas and Delta, do not contract their maintenance out to other companies. Rather, they have their own MRO facilities at the airports they operate from, servicing only their own aircraft.

Because these facilities are often located at their major hubs, airlines will specifically route planes that require maintaining, repairing, or overhauling to land in the airport housing the facility to minimize the downtime of the aircraft and its associated costs.

Whilst not that common, some regional airlines do indeed own their own MRO facilities. The primary difference between regional and major airline MROs is simply size and scope; regional airlines typically have one MRO at their main base, whilst major airlines will have MROs across all their major hubs, and many of their hubs too.

Defense MRO Companies

Whilst the USAF may be the most famous branch of the military for their aircraft ownership, all branches of the military operate their own aircraft. Some are small, some are large, some have fixed wings, others, rotary. But they all have top secret weaponry and equipment, which means they can’t just be flown to the nearest MRO.

Indeed, the threat of sabotage, espionage and even national security necessitate the need for the military to have their own MROs to do their own maintenance, repairs and overhauls. Whilst much of this is done in-house, there are a number of private sector firms contracted by the military to maintain, repair and overhaul sensitive equipment.

What Is the Difference Between MRO and AMO?

In aviation, an AMO is an Approved Maintenance Organization. This is a separate organization that performs aircraft, engine, and propeller maintenance whilst operating under state-approved supervision (by comparison, MROs just have routine supervision).

What is the Difference Between FBO and MRO?

A fixed-base operator is a commercial business that has been granted by an airport the right to operate and provide services such as flight instruction, aircraft maintenance, aircraft rental, parking, hangaring, and fuelling.

The Importance of MRO

The primary goal of any aviation MRO organization is to ensure the safety and airworthiness of aircraft. The three areas where MROs are most important are:

• Safety
• Efficiency
• Compliance with FAA regs

Aircraft regulations dictate that aircraft operators need to keep their aircraft well maintained to keep their flying certifications (known as “Parts”). To that end, airlines emphasize regular visits to an MRO facility for all their aircraft throughout the year, not just when legally required.

After all, the last thing they want is a plane crash and their name splashed on the front of every newspaper in the world.

The job of an MRO technician is to discover a potentially serious issue when it is still a relatively minor one, and more importantly, fix it. This therefore reduces the possibility of any kind of mid-flight malfunction or at worst, crash.

But MROs also act in the best interests of airlines’ bottom lines too. By ensuring all their aircraft are in tip-top shape and everything is running smoothly and efficiently, airliner fuel burn rates are as low as they could possibly be. Lower fuel burn means lower fuel cost for airlines, and thus, more profit.

Likewise, regular maintenance of an aircraft - like any machine - increases its service life, providing the airline with a constant stream of revenue for much longer.

And most importantly, visits to MRO facilities are required in the regs. These regs apply whether you have one aircraft or one hundred, and airlines can get in a whole world of hurt if they don’t follow the regs.

MRO Impact on the Aviation Industry

With thousands of aircraft engineers and technicians working in facilities and hangars in the U.S. and around the globe, MROs are a major source of employment within the aviation industry.

In 2022 alone, the global MRO market was valued at a staggering $730.09 billion! What’s more, is that it is estimated to grow 2.4 percent annually between 2023 and 2028, where it will reach a value of $839.19 billion.

Much of this growth will be driven by increased demand, as operators and airlines alike try to minimize downtime and increase the lifespan of assets by maintaining and repairing aircraft. For both the airline or operator and aircraft MRO, this translates to higher revenues, and hopefully, higher profits.