When creating a flight plan, what criteria is used to select waypoints?

Edited March 21, 20215 yr by hedbonker

Do you ask about Flight Plan Calculation Tool maybe?

This tool calculates path between 2 (or more) chosen waypoints, you can choose altitude, kind of airways (all/jets/victor/avoid RNAV option + oceanic tracks) or Radio navigation method depend on your choice.
Then you can choose if you want to create path only via airways (not always possible) -> left boundary option on slider or only via direct points (shortest path between two points) -> right boundary option on slider or another route/path that is between these options.

If you ask about real flight plans - there is also necessary to add proper points for SID (last point of SID procedure) and for STAR (first point of STAR procedure)  and create/calculate flight route between these 2 points.
If doesn't  exist SID for departure or STAR for arrive then usually as first/last point it's taken the navigation point that is closest to airport (usually this is VOR/NDB  or fix for transition/feeder approach segment).

In general, creating of good real flight plan is a kind of "art".  It isn't so difficult as it seems but it's necessary to make many flight plans to get experience. The more the easier later 🙂
There are some Internet pages about flight planning and real flight plans - you can find them via Google.

Regards,
PIotr

Edited March 21, 20215 yr by ppgas

A few more technical details:
It all depends on the slider position (34.6.7. Prefer) as PIotr explained and the selected cruise altitude.

Airways are only selected if the travel is not against a one-way direction and if the chosen cruise altitude does not violate airway restrictions (min and max altitude) of an airway segment. Jet or Victor are used as selected by the user. Some more details in the algorithm avoid airway hopping and other issues.
Therefore, the result might not look optimal and in some regions (e.g. Italy above FL310) it might be impossible to find a route.

LNM selects waypoints if no airways are found or result in large detours (slider again). In this case it uses only waypoints which are not a part of a SID/STAR, do not belong to an airport and are named. Additionally it uses unnamed oceanic waypoints like 5520N or 06W60.

Alex

 

I've forgot to write that LNM is based on Navigraph data, so if someone is a fan of flying "as real as it gets" and want to get real world flight plan it's necessary additionally verify route via external sources  because temporary closed and opened areas/airway/CDR routes etc aren't written in LNM/Navigraph  database (they can change everyday and are available in daily CRAM reports).
For EUROCONTROL area (Europe + some countries around) it's possible to use/validate flight plan against  IFPS validation tool that is free available on the page: https://www.public.nm.eurocontrol.int/PUBPORTAL/gateway/spec/index.html (right bottom -> link to IFPS tool).
The EUROCONTROL covers this area: https://ansperformance.eu/definition/eurocontrol-area/

For other areas/countries I don't know such free tools. If someone knows something about, please write - I'm interested in this subject 🙂

Regards,
Piotr

Edited March 22, 20215 yr by ppgas

Thanks so much, PIotr and Alex!  Very helpful.  I was talking really about both LNM and real life.  The question arose when I had LNM generate a plan and it chose 2 waypoints between the depart and dest locations but there were a lot of choices it could have made with little impact to the route and I just wondered how it chose those and indeed what a real pilot uses as a criteria for doing the same thing.

Edited March 22, 20215 yr by hedbonker