What Is A MEI?

What an MEI Actually Is

On this site, MEI stands for one thing: the Multiengine Flight Instructor Rating. It is an added rating on a flight instructor certificate, issued under the authority of the Federal Aviation Administration, that lets a certificated flight instructor (CFI) provide instruction in multiengine airplanes. Many other credentials in other industries share the same three letters. None of them are covered here, and nothing in this article applies to them.

If you are new to the topic, think of the MEI as an extension of skills you already have. You hold a flight instructor certificate, you hold a multiengine rating as a pilot, and the MEI is the added privilege that lets you teach others to fly those aircraft. Related explainers on this site cover the shorthand from different angles, including what MEI certification is and what MEI stands for.

The Standard Behind the Rating: FAA-S-ACS-25

The yardstick for the checkride is the FAA-S-ACS-25 Flight Instructor Airplane Airman Certification Standards, published in November 2023 and effective May 31, 2024. The Airman Certification Standards (ACS) document tells you, task by task, what knowledge, risk management, and skill the evaluator expects you to demonstrate. It is the single most important document for MEI preparation because it defines the scope of what can be asked.

Two points are easy to get wrong:

• The ACS organizes content into 14 Areas of Operation. These are overarching headings, not exam domains with published percentage weights. Anyone quoting "Domain 7 is worth a set percentage" is not drawing from the ACS.
• Not every Area is universally required for every applicant. Which Tasks you must be evaluated on depends on the ratings you already hold, as explained below.

The FAA publishes the standard on its ACS page and as a downloadable PDF for the airplane flight instructor. Reading it directly, rather than relying on summaries, is the best habit you can build. For a full walk-through of how the Areas break down, see our complete guide to all 14 content areas.

The 14 ACS Areas in Plain Language

The ACS lists these 14 Areas. We refer to them as domains on this site because that is how most candidates think about them. Here is what each one means for someone adding a multiengine instructor rating.

How the Additional Rating Table Shapes Your Checkride

This is the part most candidates overlook. The ACS includes an additional multiengine instructor rating table on printed page 98. It determines which Tasks the evaluator must cover, depending on the ratings and privileges you already hold on your instructor certificate.

Three rules govern how it works:

1. The required Tasks vary according to your existing ratings.
2. If your held ratings point to different requirements, the least restrictive one applies.
3. The evaluator may still assess remaining Areas or Tasks beyond the required minimum.

Eligibility prerequisites, endorsements, and experience requirements are a separate topic, covered in MEI requirements and how to qualify.

Knowledge Tests: AFA, FIA, and What Applies to You

Knowledge testing for instructor ratings is a place where myths spread quickly. Here is what the FAA Testing Matrix (revised September 25, 2026) indicates, with the applicability caveats that matter.

Several qualifications are worth keeping in mind:

• The listed question counts exclude optional unscored validation questions, but testing time includes them.
• Added-rating tests are not for holders of only a sport instructor certificate.
• Under 14 CFR 61.191(b), an exemption exists for the fundamentals of instructing knowledge test. It is not a blanket exemption from every knowledge test.

Because applicability depends on your certificate history, the safest approach is to check the current testing matrix and your instructor or evaluator before booking anything. For fee and cost mechanics, see our MEI certification cost breakdown, and for timing questions, MEI exam dates and scheduling. For how scoring works, read what you need to pass.

What You Must Master in Multiengine Operations

Domain 13 is where the MEI separates itself from a standard instructor certificate. The evaluator is looking for two things at once: your own precision flying a multiengine airplane, and your ability to teach it safely.

Technical topics to know cold

• Engine-out aerodynamics: asymmetric thrust, yaw, and the effect of bank on control and climb performance.
• Critical speeds: the V-speeds that govern engine-out control and performance, and how to explain them to a student without rote memorization.
• Systems: propeller feathering and unfeathering, fuel crossfeed, and electrical and hydraulic redundancy for your specific aircraft type.
• Performance: single-engine climb capability, which can be marginal or nonexistent depending on weight and density altitude.

Instructional topics specific to the rating

• How to brief a simulated engine failure so the student knows exactly what will happen and when.
• Safe altitudes and configurations for training engine failures, and the instructor's responsibility for recovery.
• Recognizing when a student is behind the airplane and intervening before a training scenario becomes a real emergency.
• Debriefing in a way that reinforces decision-making, not just procedures.

Because Domain 13 draws on other domains, especially Domain 12 (Emergency Operations) and Domain 10 (Slow Flight, Stalls, and Spins), expect overlap rather than clean boundaries. For a candid look at how demanding the process can be, see how hard the MEI exam is.

Who Hires Multiengine Flight Instructors

An MEI is a professional credential, and the employers are straightforward to identify:

• Flight schools and academies that operate multiengine trainers and need instructors to deliver multiengine add-on and commercial multiengine training.
• Part 141 and Part 61 training operations building out professional pilot programs.
• University aviation programs that include multiengine training in their curricula.
• Corporate and charter operators that need recurrent or transition training for pilots moving into twin-engine aircraft.
• Independent instructors who teach in privately owned or club-owned twins.

The MEI is often a stepping stone as well. Many pilots add it to build multiengine flight time while teaching. For more on the job landscape, see MEI jobs, and for an earnings discussion, the MEI salary guide. If you are weighing the investment, is the MEI certification worth it lays out the trade-offs.

Sequencing Your Preparation Around the Domains

Rather than a generic study calendar, sequence your preparation by how the domains build on each other. This one-time plan ties each phase to specific content.

If you are weighing how long to allow, adjust the pace to your flying currency and teaching experience. A more detailed approach is in our MEI study guide, and a quick-reference summary is available in the MEI cheat sheet. To test your recall against realistic questions, use the MEI practice test.

Where to Go Next

This article covers the definition and structure of the rating. Depending on your next question, these resources go deeper:

• Data-minded readers can see what the data shows on pass rates.
• If you want training pathways, see MEI training.
• For alternate phrasings of the same question, see What Is MEI?, MEI meaning, and what MEI means.
• Broader context on the credential itself is on the MEI certification page.

When you are ready to check your knowledge, the main practice test site offers question practice aligned to the content areas above.

Frequently Asked Questions