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I've found I see a somewhat larger area if I go to Rendering Options and tick "Extended DSF Scenery".
In any case, to see that information for an airport arbitrarily far away, try going to SkyVector and just entering your two airports in the flight plan, and looking for a label on the leg on the map.
Of course for distances much greater than X-Plane's initial map area, you'll start to see the Great Circle effect where you need to change your heading, and really to fly such long legs "direct" is unrealistic anyway; in real life airways and waypoints are used (which SkyVector can help you with).
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