I was intrigued by the every growing list of airports in Aerofly's airport database. So I clobbered together a quick visualization:
My first approach made my browser a stuttering mess, but after some fiddling with MapBox I would like to present to you:
The map is now part of the Missionsgerät, and can be used without actually entering a flight plan. So if you are on the go and like to know if an airport exists in AFS4, here you go.
Great map. Can you show the handmade airports in a different colour?
Dear Armitage
Great, it works.
If you have a bit of time to help me to embed an imported flight plan.
I don't understand what to do: "The Aerofly Missionsgerät converts Aerofly FS 4's main.mcf (and other flight plan file formats) into a custom_missions_user.tmc file (and other flight plan file formats), using your current flight plan and other settings to generate a shareable mission."
My aim is to create a flight plan with Navigraph > export it as a MS FS2020 .pln file > import it in Missionsgerät (it works, including the SID, STAR, TRANS, APPR points) > embed it in Aerofly FS 4 to fly it. Knowing that most of the waypoints of Navigraph (AIRAC 2401) are unknown from the Aerolfy data base (~AIRAC1301).
Thank you.
Great map. Can you show the handmade airports in a different colour?
Actually I am trying to improve on the rendering of the airports. I am still learning on how to use MapBox Studio, but today at least I fixed the font issues.
Stay tuned for even nicer airport symbols. 
My aim is to create a flight plan with Navigraph > export it as a MS FS2020 .pln file > import it in Missionsgerät (it works, including the SID, STAR, TRANS, APPR points) > embed it in Aerofly FS 4 to fly it. Knowing that most of the waypoints of Navigraph (AIRAC 2401) are unknown from the Aerolfy data base (~AIRAC1301).
Actually this is more or less everything you need to do:
FrankLFRS Does this help you? Or is there any other explanation missing I might supply?
And indeed this method should allow to import fixes and waypoints into AFS4 which it does not have - because the Missionsgerät will import waypoint names and geo coordinates and convert them into Aerofly's free form waypoints. A smart way to have Navigraph data at least for your flight plan.
Does this help you? Or is there any other explanation missing I might supply?
Yes it worked, thank you.
I had to create the missions folder before copying the custom_missions_user.tmc file.
It's not elegant (not your fault), but it works: hard to retrieve the mission among many, the plane is in middle air at launch, etc. But it works including unknown waypoints, and as expected, no constraints in the flight plan.
Loading a .tmc or a .pln file from the navigation menu is a hope from IPACS.
the plane is in middle air at launch
Well, maybe I can do something about it. Is there a way for me to obtain the pln you were using? I can take a look if there is some clever way for the Missionsgerät to improve the starting point.
Is there a way for me to obtain the pln you were using?
Here it is.
I renamed it as a .txt file to be downloadable here, but, it is a .pln file as a MS FS 2020 flight plan from Navigraph.
The flight plan includes the runways, so if there's a way to include them... [edit: but some runways number will not fit Aerolfy's]
Thank you for taking care of it.
On the Mac, I intend to do:
- Creating a flight plan with Navigraph;
- Exporting it as a .pln file;
- Converting it as a .tmc file;
- Importing it using a magic script to a custom_missions_user.tmc;
- And, fly it
And, I will make do without constraints, and without STAR and without SID (they exist anyway as a suite of points, and by the way, I will avoid the autopilot fails to follow them).
A complex one: Nantes > Geneva.
The arrival:
In green a waypoints of the STAR that turns around from INDIS to go back to INDIS to intercept the ILS.
I didn't try it yet in Aerofly 
!
FrankLFRS Thank you for your input and testing. I fixed the bug where the flight plan would start you aircraft up in the air on importing pln flight plans. You are now starting on the ground.
I also improved the documentation - this helps to understand how to use the map to fix the start position of your plane by dragging it to the right spot. (This is actually a trick I used to modify my jet flight plans to fly through narrow valleys.)
The runways get read by the Missionsgerät, but it does not yet create the waypoints necessary for Aerofly FS4, as they need to match names known to Aerofly FS 4 (at least the last time I checked). As the magnetic heading of runways has changed in the last few years, some runways are today named differently from the names used by Aerofly. But maybe I come up with another idea on how to fix this.
Dear Armitage
Thank you for all the care.
I will give up the idea of using Navigraph because it is not integrated to Aerofly. And especially because the .pln export file does not include the approach waypoints (under AIRAC 2401 the RNAV to Innsbruck can be flown to the runway, same with Aspen, etc. which is not possible today in Aerofly). And after all of all, the latest waypoints, those from the approach, are the most important and the most missing in Aerofly today.
Thank you, keep on improving Missionsgerät...
I think I killed EDDB with my tests with LFBO-EDDB.
It's impossible to SID, STAR and APPR at EDDB.
(custom_mission_user.tmc deleted)
Thank god you found out that the custom missions did not kill you navigation database. I was slightly concerned. 
The best solution definitely would be if all current SID, STAR and other procedures would be right inside Aerofly. IPACS mentioned the prohibitive costs of this option, so let's start a fund raising.
Second best would be to load flight plans (pln, fms, tmc) via a small dialog directly from thr navigation screen in Aerofly. I remember that IPACS liked the idea, so let's keep our fingers crossed.
Thank god you found out that the custom missions did not kill you navigation database. I was slightly concerned.
I was about to write it to you to make you comfortable.
The best solution definitely would be if all current SID, STAR and other procedures would be right inside Aerofly. IPACS mentioned the prohibitive costs of this option, so let's start a fund raising.
It must be very expensive, for example, Navigraph is almost 11€ per month.
Second best would be to load flight plans (pln, fms, tmc) via a small dialog directly from thr navigation screen in Aerofly. I remember that IPACS liked the idea, so let's keep our fingers crossed.
I do agree at all. Because I am used to using http://onlineflightplanner.org/ with AIRAC1301, and I would be able to enter the route in one click.
Thanks for all.
