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Is this normal?

Marc Stanford

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Marc Stanford

I noticed on flight plans with Simbrief it will make me do a descent and then back up to the normal cruise altitude, is there any reason for that and does it happen IRL?

Screen Shot 2020-07-25 at 5.48.56 PM.png

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I think it is due to the ONE rule (Tracking 000 to 179 fly ODD level, EVEN level o.w.). Not sure about how the real world route would be filed in this case.



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Does happen IRL. At least in Europe, airspace contains quite some complex restrictions, and sometimes such ”yoyos” happen in flight planning, but I believe they are not actually flown all that often, i.e. ATC will actually allow you to maintain the level.

Another reason might be more favorable winds/atmospheric conditions on the lower level, but looking at the graph that doesn’t look like the case here.

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Mateusz Chalupniczak

This happens becuase some waypoints and as well as airways only exists in certain flightlevels or are temporarly restricted. [or errenous routing segment]

The best example is Europe where most of the airways have coresponding "upper" airway above ~~FL260. So if you want to fly lets say L869 your "automatic" highest picked level will be 260. But if you insert "u" before (UL869) you will be able to cruise at ie. level 340.


I've checked your routing and it looks like you have between IDOSI and ARROW an incorrect direct segment. [edit] Direct segment is correct but simbrief doesn't have it in its database most likely.  That's why it result in this erreneous level.

What I was doing back when using simbrief was inserting special "command" to the routing. In your case it should be IDOSI/N0450F341. N____ means expected crusing speed, F___ is requested flight level.

I'm not sure if chinese system will allow flight levels in feets.


And no it's not a bug

No, it has nothing to do with 0-179/180-359 rule. 

And yes, things like this happens IRL but it's very very very rare and doesn't  happens MID CRUISE. If dispatcher would pass this flight plan forward he would be likely fired.  

If it were to happen it would be during descend if not aircraft would fly different route.

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