A little refresher on cruising altitudes!

Happy Wednesday, everyone! Today, I was flying and I noticed something that seems to constantly re-appear every time I take to the Infinite Flight skies. This is the concept of cruising altitude and how you should decide your cruising altitude when planning a flight.

Many people on Infinite Flight seem to choose to fly at any altitude they want, which is acceptable.

But, on the expert server, of all servers, I would expect pilots to have a little bit more common sense and follow this very simple guideline!

These are the cruising altitudes you should fly at based on your heading (both IFR and VFR):
Source #1 (image) Source #2 (FAA)

If you are flying at a heading between 0 and 179 degrees, you should be cruising at an odd flight level (ex. 15,000 feet, FL330, FL290, etc). If you are flying at a heading between 180 and 359 degrees, you should be cruising at an even flight level (ex. 16,000 feet, FL340, FL 360, etc.)

Today while I was flying between Auckland and Sydney at a heading of 260 degrees and a cruising altitude of FL360, I noticed there was another pilot heading directly at me from in front! I immediately began to descend and they passed over the top of me with about 500’ to spare. This just goes to show how important it is to follow the “altitude based on heading” rule!

Quick summary:

If you are flying a heading of 0-179 degrees, cruise at an...

ODD altitude (FL330, FL310, 19,000 feet, etc.)

If you are flying a heading of 180-359 degrees, cruise at an...

EVEN altitude (FL320, FL380, 16,000 feet, etc)

I hope everyone can learn a little something from this post and remembers it for the future!


Thanks for reminding us ! kinda gets confusing because some people don’t follow that rule and you might think you are in the wrong.


Dont know if that counts Also when you get to chinese airspace your altitude might need to go up around FL311 (31,100) and the same thing in odd and even altitudes


yup that’s correct, same with Mongolian airspace too
I wish more ppl knew that as I’ve never seen anyone else following that rule when flying in China


Also, some countries have different semi-circular guidelines. For example, France often use a North/South version apposed to East/West. And it is not a rule, it’s a suggestion I’m pretty sure.


This should probably go in #ground-school:community-tutorials, but idk

Nah I didn’t create it as a tutorial, just a mere reminder about the guidelines :)


Thanks @Cannoli928 for this!

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That’s just cuz people go AFK
And IFATC can’t give metric altitudes

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There are quite a few exceptions actually: Over oceanic airspace ATC can often clear aircraft to any altitudes because there aren’t a lot of planes. Semicircular rule does not apply at all over the north atlantic. Some countries use north-south rule.

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Good to know, I like this, will keep this in mind

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The east-odds and west-evens rule is not enact over the North Atlantic Tracks (NATs), it is generally the opposite, I suggest checking the daily altitude info on them on skyvector.com.

It’s not in effect on the tract or not IIRC.

My source was the FAA website, therefore I was talking about America. I guess you are right, though, and I would like to hear what the Infinite Flight staff would have to say about it! I’m going to reach out and see.

Tracks have altitudes assigned to them and this isn’t what I’m talking about

Pretty sure IFATC center is not to intervene with semicircular issues unless a conflict develops.

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Always worth a reminder! Our ATC Manual also says that radar controllers are responsible for ensuring aircraft are at the correct altitude for direction of flight. 🙂



Always nice to remind this to everyone, but I have a little doubt…

Aren’t FL310 and FL350 an odd Flight level? Why are them between 180° and 359°

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There is no need to have any doubt whatsoever! The User Guide states that these rules apply, take a look at the section labeled “IFR/VFR Semi-Circular Rules” on this link :) https://infiniteflight.com/guide/flying-guide/take-off-to-cruise/step-climbs-and-cruising-altitudes#ifr%2Fvfr-semi-circular-rules

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From this article:

“In the past, aircraft flying between the surface and FL290 needed 1,000 feet of vertical separation, but anyone flying above FL290 needed 2,000 feet of separation. The reason was simple: the accuracy of pressure altimeters decreases the higher you go, and at the time, altimeters weren’t accurate enough to guarantee adequate separation between converging traffic.”

This meant that eastbound aircraft would fly at FL290, F330, FL370, etc. Westbound aircraft flew at FL310, FL350, etc.

Now that technology is more advanced, the implementation of RVSM allows for pilots to have 1000ft of vertical separation instead of 2000ft. The FAA’s 7110.65 also references the difference in servicing RVSM and non-RVSM aircraft:

“Apply 2,000 feet at or above FL 290 between non-RVSM aircraft and all other aircraft at or above FL 290.”
~4-5-1, Vertical Separation Minima

Based off of research, I would assume that most modern aircraft are RVSM-approved. You can check out the following source for approved operators in the United States, Canada and Mexico. :)