How to determine correct cruising altitude?

I know when you’re in the world map making a flight plan you can look a the nav log and it’ll show you the correct cruising altitude. However once you’re in the cockpit the nav log no longer shows this. Is there another way to determine the correct cruising altitude once you’re already in flight?

There is no such thing as a correct altitude. In actual flight planning it will depend on a multitude of factors.
If you are looking for the even–odd rule, in many countries you‘d fly odd levels going on headings 0–179° (5000‘, 7000‘, FL310, FL330…) and even levels going 180–359° (6000‘, 8000‘, FL360, FL400…). For VFR you’d add 500‘.
If you look at a suitable altitude performance or airspace wise then things get more complex.


Ah yeah, I was wondering if there was a sweet spot for performance, but it sounds like you’re saying it can change from aircraft to aircraft, right?

I guess I was leaning on my knowledge that commercial flights typically fly between 31,000 and 38,000 feet. So I was wondering if there was an optimal range for propeller planes.

The correct cruising level can get very complex in certain regions. Airlines rely on complex flight planning software with certain rules built into the navigation data. The information is taken from individual countries AIP’s. Some of these you can get access to for free and others not. Im pretty sure IVAO gives region specific info which may help.

You can either take the cruising altitude that the flight plan gives you in the sim or you can change it to reflect your personal flight planning. This is going to depend on the type of aircraft, IFR or VFR flight plan, winds aloft, and other factors.

You can look up the optimal ranges for the propeller aircraft you want to fly and go from there. If you are wanting to be realistic that is. Generally though the propeller aircraft without oxygen are not going to cruise above 10,000 ft. (ballpark). Turboprop aircraft with oxygen and/or pressurization can get into those higher altitudes but you would have to look at service ceilings and performance tables to see where the optimum altitudes would be. Then look at winds aloft forecasts and adjust from there.

The even-odd rule mentioned is correct and for VFR you add 500’ up to FL180. There is no VFR flight above FL180 (18,000 ft.)

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Another option to the OP – get a simbrief account (it’s free) and it does the flight plan for you, including the altitude/speed/etc. Very useful.

Oh wow, SimBrief seems really in depth!

Here’s a video tutorial I found on it for anyone else that’s curious.

Depends on the plane. For the airbus and 745 there are some factors to consider.

Let’s take the Airbus A320 for example> we could say the average is 35,000 feet however i reality their are other aspects. Climbs on such planes including the 747 are gradual of a period of time. Gunning engines to get up high is not fuel economic.

Factors: Flight distance.
Weight on plane including Fuel, passengers Cargo.
Weather, Cloud ceiling, wind sheers.

A320 ratings: (Speed and alt)
Max cruising speed 903km/h (487kt) at 28,000ft,
economical cruising speed 840km/h (454kt) at 37,000ft.

Lift versus weight is important. More, you fly lower, less weight you can cruise higher.

Minimal Alt recommendations not on long trips: probably 10000, can cruise 12000-15000feet
Longer trips, and can reach the optimized cruise alt. 20,000 to 35,000, 45,000 in weight displacement

Game wise for a decent trip let’s average about 35,000 feet. Short about 12000-20000, mid 15000 to 25000.

IF cloud ceilings are 36,000+ feet Don’t even attempt to fly over it. You will have to drop alt below the ceiling. Going through moisture does create drag and is not economic. IF you can get over and cruise 35,000 to 40,000 feet, that is good, and the lift will be their. if not and you are popping through alot of moisture, don’t and drop below the cloud bank.

If setting it in your plane. Set the cruise 25,000 on a decently long trip over 3-5 hours unless you know weather will be bad with high storm banks. IF going more then 6 hours Sure cruise at 35,000

Uhm, I tend to disagree with quite a lot up there, if we’re talking jets here.

First of all, of course it is fuel economic to climb as high as possible. Jet engines run a whole lot more fuel saving at altitude. Example: even on a short flight of <1hr I’d climb up to FL410 if the weight permits (talking about real life here). That might very well be the FMC calculated optimum altitude in such a case at low weight. The cruise portion might be very short then, with the T/D being not long after the T/C. Depending on the aircraft there might even be a number deep in the FMC called something like minimum cruise time to determine its optimum altitudes etc., and this might be as low as one minute. Just so you have an idea how „short“ you could realistically be in cruise. However, the level might also be as low as FL240ish, but then mostly due to airspace considerations. Lot less efficient down there.

If the flights are longer and you have payload to carry we’d be somewhere in the 350—390 range, simply because of weight.

I have never in my life heard anything about flying through moisture having an effect on flight planning, at least if we’re not talking about CBs or icing issues and maybe avoiding those areas.

And of course do we climb above clouds >FL360. In fact you’d even climb higher if performance permits for a smoother ride if you were riding the tops.

Last but not least, if you are talking about cruising at FL250 on 3—5hr flights (!) you’d burn tons, tons of fuel that is just going to waste. There are malfunctions that would dictate such a low level even with these flight durations (think of pressurization…), otherwise this is completely unrealistic.


how are you guys calculating your altitude? let a flight planner such as simbrief to determine it? or you make your own calculations and decide your appropriate altitude? (just curious to see the different options out there…)

I use Simbrief as I have no idea how to calculate it myself. If I was doing A320 flights I could just pick a low FL30x’s altitude since that’s pretty obvious based on real flights I’ve been on, but anything else I’m lost instantly other than knowing the max altitude as per the aircraft selection pages.


It should be based on aircraft performance charts, then modify for hemispheric cruising rules/airspace rules, then weather.

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Could we trust Simbrief flight level when set on AUTO?

I was planning a flight LOWW - EFHK, simbrief recommend FL360
As the average heading is around 020 I was expecting FL350 or 370.

So should I trust Simbrief?

Hi, as an airline pilot, I can agree that there are tons of factors to be considered, especially flying IFR and jet engines. One is performance: on very short flights the general rule is calculating a flight level as high as possible that leaves a section of five minutes at level flight in that cruise level, but as also mentioned the optimum flight level does change with weight, prevailing winds and temperature. The heavier the aircraft, the lower you fly. If you can get your hands on the performance handbook of your aircraft you have many, many tables you can use. However, a modern jet should be able to indicate its optimum cruise level to the pilot, especially if fed with good wind data for the different flight levels and the altitude of the tropopause.
Then comes the question of airspace structure. Most countries use that semicircular rule that was mentioned before, others (especially those that have a much bigger N-S extension than E-W) turn that semicircular rule by 90 degrees. Furthermore, using airways, that rule may once again be flipped on its head for certain airways. Here, you may want to consult each (!) of the overflown countries AIPs.
And then of course there’s always the question of the minimum enroute, offroute altitudes as well as the minimum usable flight levels (MUFL).
Modern briefing systems take care of all of these and are good in calculating a very reasonable sequence of flight levels (remember, as fuel is burnt, the weight decreases and the optimum rises), provided that the actual weight and weather match the planning conditions to a high degree.
How well Simbrief does that? No idea, I use MSFS only to fly VFR.
All in all: there is virtually no limit when it comes to perfecting flight planning and execution. Look for the best compromise for your needs and wishes when it comes to SIM-flying!

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Simbrief has never failed me on most flights except extremely short sectors in an airliner. Sometimes it plans at altitude that is too high, so that you never actually reach cruise.

I find that on certain airliners, like the 747, it sometimes plan an altitude that is too low when it might be better optimized to climb higher given winds and fuel economy. However, thats normally not an issue since one can request higher enroute.

A good rule of thumb though, especially if you are doing short sectors, is to take your distance and base off your final altitude from that. For instance, if you are flying a 150 nm leg, then I wouldn’t go higher than 15000’. But this is mostly for shorter sectors. Longer sectors, you take into account the weight of the aircraft, winds, temperatures, and airspaces into account. I generally try to comply with westbound/eastbound altitude cruising orders as well, although certain airspaces and airways may be more specific on such matters.

This is all talking about jets of course.

I once asked this question to a 737 airline pilot who flew mostly short legs. He said as a rule of thumb, minimum 5 minutes on cruise (from TOC to TOD).

Thank you very much for your detailled answer, it helps a lot.

I’ll try to optimize on VATSIM or IVAO, in particular when my flight is going through Italy or Portugal as they have a North Sud Semi Circular rule.