I give you two cities. If you were to draw the shortest line between the two, what country (other than the ones in which the cities are located) would you pass through.
In the instructions, please specify which projection you're using (Mercator I assume?). Also, the shortest route used by airplanes is not a straight line on a map, so specify loxodromy, not orthodoxy.
If you're talking about a *straight line* on a map, as opposed to the actual *shortest path*, the line depends on the projection. The right way to calculate the shortest path is by a great circle, which is not generally a straight line on any projection. So I agree with the commenters who recommend specifying the shortest route, which is a great circle, and which is independent of any two-dimensional map projection.
In the instructions, please specify which projection you're using (Mercator I assume?). Also, the shortest route used by airplanes is not a straight line on a map, so specify loxodromy, not orthodoxy.