Even though there is no fields in common, the easiest way to do this is to union the data (maybe even outside of Tableau).
When doing mapping the way you want, you have to use a common latitude field and a common longitude field. You can't use 2 different fields and you can't use the Tableau generated ones.
Do you have some sample/dummy data you can post and I can show you how to do it.
Ah, now I see what you're trying to do
I'd forgotten that Airport Code is a geographic role, but this is where you're getting stuck - you can't use the Tableau generated lat/long values as well as your own lat/long values on the same map.
It will work if you can get the lat/long values for each airport (that wouldn't be too hard) and then create a common dimension with those. It's still a union, but the lat & long fields are the common fields (ie in both datasources)
I currently have also an issue with flight routes.
As Tableau now has the IATA airport codes as a geographic role I assumed that I can use this to display the flight routes as lines when applying the normal path logic of Tableau. But in all the examples with similar visualizations there are longitude and latitude values in the used data.
Does this mean I have to provide longitude and latitude values in my data and can't use the generated values when wanting to visualize the flight routes as lines ?
Thx for your feedback on this.
I don't know for sure, but I doubt you can use Tableau's internal lat/long to do this