To answer the original question, the idea that a flat earth map could be produced that someone could navigate by is an impossibility.
Have you assessed all possible layouts, continental configurations, jet stream paths, navigational assumptions, to make that statement?
Not necessary. Take four points reasonably far apart from each other, then measure the six distances between them. Geometry will do the rest. If earth is not flat, the distances between these points will not be consistent with the distances calculated on the assumption it is flat.
That's true but few flat-earthers will accept those distances as accurate. That is why so many try to estimate distances from aircraft flight times.
This from an earlier post and uses great circle distances:
For example take the international airports at Johannesburg (JNB), Dubai (DBX), Beijing (PEK) and Sydney (SYD).
The nominal distances between these airports (from
Great Circle Mapper) is:
| | DBX | | PEK | | SYD |
JNB | | 6,390 km | | 11,699 km | | 11,045 km |
DBX | | xxx | | 5,857 km | | 12,039 km |
PEK | | xxx | | xxx | | 8,934 km |
Now if we take the Johannesburg (JNB) to Sydney (Syd) flight (11,119 km) as a baseline we can use
the routes JNB to SYD, JNB to DXB and JNB to DXB to calculate the location of Dubai, relative to Johannesburg and Sydney and use
the routes JNB to SYD, JNB to PEK and SYD to PEK to calculate the location of Beijing, relative to Johannesburg and Sydney.
Then the distance from Dubai to Beijing can be calculated or scaled off a diagram - I did both.
This shown here:
JNB-DBX-PEK-SYD Flat Air Routes This distance from Dubai to Beijing is 7,608 km
calculated in Excel.
But the actual air route distance from Dubai to Beijing is not 7,608 km but 5,857 km.
So these flight distances do not fit on any flat surface.
Now the distances I have used are just the nominal distances and real flight distances would all be a little longer.
Some other kind person might like to go to the trouble of looking up actual flights on
FlightRadar24 or
FlightAware, QANTAS QFA64, JNB to SYD