In the Data menu you should see an option to convert to custom sql.
Use that and it will give you the custom sql equivalent of the current view.
Copy that text and duplicate it by pasting below the first one
add a UNION ALL in between (all means keep duplicates)
For the first sql block add
,1 AS [PathOrder]
For the 2nd sql block add
,2 AS [PathOrder]
and that should do it. You really don't need to do a PathID in custom SQL. You can put both origin and destination detail shelf together or create a combined field in Tableau instead and get the same effect.
If you want to make the lines curved similar to what flight maps show you can use a larger number than 2 for the second PathOrder value and use densification.
Alan Eldridge has a good tutorial on this