MDA vs DA: What’s the Difference? (A Guide for Instrument Students)

By Alice Trent, CFII

If you’re studying for your Instrument Rating, you’ve probably come across two terms that sound deceptively similar — MDA and DA. Both relate to minimums on instrument approaches, and both tell you how low you can go before you must either see the runway environment or go missed. But they apply to different types of approaches, and the distinction is one every instrument pilot must understand clearly — not just to pass the checkride, but to stay safe in the soup.

As a CFI who’s helped many students through their instrument training, I know this topic can feel confusing at first. Let’s break it down in plain English, go through examples, and finish with a few tips to help you remember the difference once and for all.

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What Does MDA Stand For?

MDA stands for Minimum Descent Altitude.

You’ll find an MDA published on non-precision approaches — that is, approaches that don’t provide vertical guidance to the runway. Common examples include:

• VOR approaches

• NDB approaches

• Localizer (LOC) approaches

• RNAV (GPS) LNAV approaches (without vertical guidance)

What MDA Means in Practice

The MDA is the lowest altitude you’re allowed to descend to during a non-precision approach until you see the runway environment.

You’ll descend from your last step-down fix to the MDA, level off, and maintain that altitude while flying toward the missed approach point (MAP).
If you see the required visual references (like the runway lights or markings) before reaching the MAP, you can descend below MDA to land.
If you don’t see anything by the MAP, it’s time to execute the missed approach.

A Simple Way to Remember MDA

Think of the “M” in MDA as standing for “Maintain.”
You maintain the altitude — you don’t descend below it until you have the runway in sight.

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What Does DA Stand For?

DA stands for Decision Altitude (or Decision Height, depending on whether it’s referenced to MSL or AGL).

You’ll find a DA published on precision approaches and approaches with vertical guidance.
Examples include:

• ILS approaches

• LPV approaches (a type of GPS approach with vertical guidance)

• LNAV/VNAV approaches

What DA Means in Practice

The DA is the altitude at which you must make a decision:
Do you have the required visual references to continue the approach and land, or not?

Unlike with an MDA, you don’t level off at a DA. You’re on a continuous descent path (guided by the glideslope or glidepath).
When you reach the DA and don’t see the runway environment, you immediately initiate the missed approach — no delay, no level-off.

A Simple Way to Remember DA

Think of the “D” in DA as standing for “Decision” (because that's literally what is is). 
At DA, you make a decision — land or go missed.

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The Key Difference Between MDA and DA

Here’s the big-picture difference:

In short:
👉 MDA = Maintain altitude until you see the runway.
👉 DA = Decision point on a continuous descent.

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Why the Difference Matters

1. Flying the Wrong Technique Can Be Unsafe

If you try to “dive and drive” (descend quickly to MDA and level off) on an approach with a DA, you’ll blow through the glideslope and destabilize the approach.

If you try to fly an MDA approach as if it had a DA (continuing to descend below MDA without visual contact), you’ll risk hitting obstacles below the protected area.

Each type of approach has a different level of terrain and obstacle protection, and it assumes a specific technique. Fly them correctly and they’ll keep you safe.

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Example Scenarios

Let’s look at two quick examples to visualize how this plays out in real life.

Example 1: VOR Approach to Runway 17

The chart says:

• MDA: 1,200 feet MSL

• MAP: 1.2 NM from the VOR

You descend from your final approach fix to 1,200 feet and level off. You maintain that altitude while watching for the runway.
If you see the runway at, say, 0.5 NM from the MAP, you can descend and land.
If you don’t see anything by 1.2 NM, you go missed.

Example 2: ILS Approach to Runway 17

The chart says:

• DA: 900 feet MSL (200 feet AGL)

You intercept the glideslope and descend steadily. At 900 feet MSL, you check: do you have the runway or approach lights?
If yes, continue to land.
If not, immediately go missed — no level-off.

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Common Mistakes Students Make

1. Confusing MDA and DA During Oral Exams

On your checkride, your DPE may ask something like, “What’s the difference between MDA and DA?”
Don’t just say, “One’s for precision and one’s for non-precision.” That’s true, but it’s not the full picture.
Explain how you fly them differently — that’s what they want to hear.

2. Leveling Off at a DA

This one happens often when transitioning from non-precision to precision approaches. At DA, you do not level off. You go missed if you don’t have the runway environment in sight.

3. Diving Early on an MDA Approach

Some pilots “dive” aggressively to MDA, which can lead to unstable approaches and missed altitude tolerances. Instead, descend smoothly from the final approach fix, aiming to reach MDA about 100 feet before the MAP, giving yourself time to stabilize.

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Pro Tip: Understanding "CDFA" – Constant Descent Final Approach

The FAA now promotes the Constant Descent Final Approach (CDFA) technique — essentially flying a non-precision approach as if it had a glideslope.
You use a calculated descent angle (often 3°) to descend continuously from the final approach fix to the MDA, reaching MDA right around the missed approach point.
This minimizes the old “dive and drive” technique and leads to a much more stable approach.

Even though the chart says MDA, if you fly a CDFA, you’ll treat that altitude almost like a DA — you reach it and either continue visually or go missed.

 

Final Thoughts from Your CFI

The difference between MDA and DA isn’t just about passing the knowledge test — it’s about understanding how instrument approaches are flown safely. Each number on the chart has meaning, and each tells you what’s expected of you at that point in the approach.

When you brief an approach, say out loud whether it uses an MDA or DA. Visualize what you’ll do at that altitude before you even get there. Doing so not only helps you stay ahead of the airplane — it helps you fly like a true instrument pilot: precise, predictable, and safe.

So next time you open your approach plate, remember:
At MDA, you maintain.
At DA, you decide.
And with that, you’re one step closer to nailing your instrument rating — and flying in the clouds with confidence.

By Alice Trent, CFII

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