For most Boeing 737 operations, Flaps 30 is the normal landing setting and Flaps 40 is used when you need a lower approach speed or shorter landing distance. Both can be correct on many 737 variants, but the right choice depends on runway length, conditions, weight and your operator’s approved procedures.
Flaps 30 or Flaps 40: which is the usual 737 landing setting?
If we answer the question the way most pilots and simmers mean it, the short answer is simple: Flaps 30 is usually the standard choice. It gives a good balance of landing performance, stable handling and go-around capability.
Flaps 40 is not wrong, and on many 737 models it is a normal certified landing configuration. It is normally chosen when we want extra landing performance, usually because the runway is shorter, the stopping margin is tighter, or the operator’s performance calculation shows a clear benefit.
The key point is that there is no universal rule saying one is always better. On the 737, the flap setting is a performance choice, not just a habit.
What is the practical difference between Flaps 30 and Flaps 40 on a 737?
| Factor | Flaps 30 | Flaps 40 |
|---|---|---|
| Usual role | Normal landing flap for many operators | Landing flap when extra stopping performance is needed |
| Approach speed | Higher | Lower |
| Drag on final | Less | More |
| Landing distance | Longer than Flaps 40 | Shorter than Flaps 30 |
| Go-around performance | Generally more favourable | Generally less favourable because of higher drag |
| Fuel burn and noise on approach | Usually lower | Usually higher |
In plain language, Flaps 40 lets the aircraft fly the final approach a bit slower, which usually reduces landing distance. The exact speed difference depends on weight and the exact 737 model, but it is commonly in the region of a few knots rather than a dramatic change.
The trade-off is drag. With Flaps 40, the aeroplane feels more “hanging on the engines” on final. That is useful when you need to get stopped in less runway, but it is not automatically the best choice when you have plenty of runway available.
Why do many 737 operators prefer Flaps 30 for a normal landing?
Because it is a sensible middle ground. We get stable approach characteristics, enough drag to land comfortably, and better go-around margins than with Flaps 40.
It also tends to be kinder operationally. Flaps 30 usually means slightly less thrust on final, a little less fuel burn, and often less noise and wear than flying every approach with full landing flap.
That is why many airline standard operating procedures make Flaps 30 the default, with Flaps 40 used when performance demands it.
When should Flaps 40 be used on a 737?
Flaps 40 makes sense when the extra stopping performance matters. Typical cases include:
- Shorter runways where landing distance margin is limited.
- Wet, slippery or otherwise degraded runway conditions, subject to the operator’s performance method and approved data.
- Higher landing weights where the calculated stopping distance with Flaps 30 is less comfortable.
- Approaches where a lower reference speed helps, provided the aircraft documentation and company procedures support that choice.
Even then, we do not just pick Flaps 40 because it feels safer. We use it because the numbers and procedures justify it.
Is Flaps 40 always safer because it is slower?
No. That is a very common misunderstanding.
Yes, Flaps 40 usually gives a lower approach speed and a shorter landing distance. But it also creates more drag, which means go-arounds are less forgiving and the aircraft can feel more speed-sensitive if the approach is not well stabilised.
Safety comes from using the approved flap setting for the actual conditions, flying the right reference speed, and staying within stabilised approach criteria. It does not come from always selecting the biggest flap angle available.
How do we choose between Flaps 30 and Flaps 40 on the 737?
- Start with the approved SOP. Check the procedures for your exact 737 variant and operator. Some treat Flaps 30 as standard; some have more specific rules.
- Run the landing performance calculation. If your performance method allows both settings, compare the landing distance margin for Flaps 30 and Flaps 40.
- Assess the runway. Length, slope, elevation, braking action and surface condition all matter.
- Consider the weather. Wind, gusts and turbulence may influence which flap setting gives the most practical and stable approach within SOP.
- Think about the missed approach. More flap means more drag, so the go-around side of the decision matters too.
- Brief the choice clearly. Once selected, the crew should brief the flap setting, reference speed and any performance limits so there is no doubt on final.
What about strong crosswinds or gusty conditions?
This is where people often expect a simple answer and do not get one. In stronger winds, many operators prefer a reduced landing flap rather than more flap, because it can improve handling margins and avoid carrying an excessively low approach speed in gusts.
That does not mean Flaps 40 is forbidden in wind. It means wind can push the decision back towards Flaps 30, or sometimes another approved reduced-flap landing configuration, depending on SOP and aircraft limitations.
So if the weather is gusty, do not assume “more flap is better”. Check what your procedures actually call for.
What should simmers do in a 737 add-on?
If you are flying a Boeing 737 in a home simulator, the most realistic default is usually Flaps 30 for a normal landing. Then switch to Flaps 40 when your landing performance calculation, runway condition or airline-style SOP makes it the better choice.
If your add-on includes performance tools, use them. If it models airline procedures, follow those rather than treating flap selection as guesswork. Real 737 crews do not choose between 30 and 40 by feel alone.
For everyday sim flying, a good rule is:
- Long, dry runway with comfortable margins: Flaps 30 is usually appropriate.
- Tighter runway performance margin: Flaps 40 may be the smarter choice.
- Gusty or strong wind conditions: check the aircraft guidance carefully before assuming Flaps 40.
Does this apply to every Boeing 737 model?
Broadly, yes, but the details still matter. Different 737 generations and different operators may have small procedural differences, and the approved data for the exact aircraft always takes priority over generic advice.
That is why we are careful not to turn this into a blanket rule. The principle stays the same, though: Flaps 30 is commonly the normal landing flap, and Flaps 40 is commonly the performance flap.
The bottom line
If you are asking which flap setting you should normally use on a Boeing 737, our answer is Flaps 30 for most routine landings. Use Flaps 40 when you need the extra landing performance and your aircraft’s approved procedures support it.
In other words, do not think of Flaps 40 as “better”. Think of it as more specialised. The best 737 landing flap is the one that matches the runway, the weather, the weight and the SOP.