Cruise Altitudes Reminder

Hey IFC,

I have seen another rise in the number of people flying and events here in the IFC that are using the wrong cruise altitudes for the direction they are flying.

Let me summarise:

This only applies if you are at 29000ft or above

If you are flying EAST (Heading 360’ to 179’), you should be flying at an ODD cruise altitude.

E.g. (29000, 31000, 33000, 35000, 37000, 39000)

If you are flying WEST (Heading 180’ to 359’), you should be flying at an EVEN cruise altitude.

E.g (30000, 32000, 34000, 36000, 38000, 40000)

Please follow this as this is what it is IRL and Infinite Flight strives for as much realism as possible!



There’s already a whole topic about it, covering what you said in your post :)



There are indeed several topics on this, but I do feel reminder can help. Here’s a picture that describes what you wrote. It ‘speaks more than a thousand words’.
This is for flying under instrument rules, which is what most of us do.


I would also like to point out that the thread you linked to has the incorrect cruising altitudes, this practice was replaced in North America, Europe and i believe most of asia. Places like africa and austrlia still use the FL310, 350, 390 practice, but NA, EU, Asia use 310, 330, 350 etc.

edit: incorrect at the 4,000ft interval graphic, everything else is good!


Dear God, yes please. This needs to be known by everyone.

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Hey @mwe2187
Thanks for the clarification. Maybe you can exchange your data with @SkyHawk_Heavy and decide together “the“ rule to apply in IF.
In fact the 2’000ft separation between parallel headings above FL290 seems to be legitimate only in the designated Reduced Vertical Separation Minimum (RVSM) airspace, which we don’t have in IF.
The 4’000 ft separation is still enforced according to the law article no. 14 CFR 91.179 - IFR cruising altitude or flight level.

Blue skies

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the odd and even is only upto FL290. above fL290 its east bound fl290 and 4000 ft intervals. like 290, 330, 370. west bound fl310 and 4000ft intervals. 310, 350, 390. also for VFR flights its +500 from IFR.

@BennyBoy the information contained in your post is not exactly correct and can be misleading.


Thanks @niks.goen . This is how I understood, too

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Yeah see this is where the rules is going to differ based on location, as @Laminar was getting to. I’m not an aviation expert but got into a conversation about this in a VA setting a few months back that made me research and find info on RVSM.

All of North America (i believe, maybe just US, Canada Mexico?), all of Europe and most of Asia fall under RVSM now which got rid of the 4,000 interval and only need 2 between aircraft flying the same direction, scarily only 1,000 between aircraft heading towards each other


Here is the faa text on it, which actually clarified that RVSM rules now apply basically around the world


@mwe2187 nice. I was not aware of it… so what is the present cruise altitudes…?

I remember this by thinking East is like Even, but it’s actually the opposite. Odd but it works.

Benne, thank you for this. Very helpful information.

A feature to force RVSM altitudes between FL280 and FL430 could really help

I had a bad story of this in ths casual server, ths guy was coming at my 12h and same altitude (I was heading West so FL360).
By myself, I choose to descend at FL350, then he saw me and begun to descent too…so I stoped my descent to climb over him…he was still at 10 miles and getting closer

but at that time, he saw climb back to FL360, and he climbed back to FL360 too !! we were at 5 miles…
when I see what he was looking for, I did a right turn (as in the air circulation rules) he didn’t changes his route then we meet at FL360 both with less than 4 miles of separation.

the guy in particular was an a380 from LHR to a destination that I forgot.

this guy was clearly looking for a colision

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Well, I feel that this is an important topic for the dev’s to take position on.
For sure we don’t want to find ourself into a similar situation which @william run into, right?


What are the rules for above FL390, as aircraft heading both east and west use FL390, 410 and 430 for their steps.

Also, a hell of a lot less crucial but for those ®️ealism fans, China and Mongolia measure altitude in metres meaning that they cruise at non standard altitudes when looked at in feet. You can usually get a correct altitude by just adding 100ft onto your normal cruising altitudes.


Why do China and Mongolia use metres. It has caused crashes (IRL) in the past because of confusion between metres and feet.

yeah, that’s right

really need something to fix that

I honestly have no idea but I’d guess it’s because China never used the imperial system in the first place so Chinese pilots understand metric measurements better. Mongolia probably just goes with China or Russia (although they now use imperial altitudes) for simplicity, however if you check on a flight tracker some aircraft cruise at imperial altitudes and others at metric.

Does simbrief use this to make fight plans?