It is a straight line if viewed from directly above. As mentioned earlier, spherical geometry 101. Actually, as I understand it, long haul flights fly straight but make periodic adjustments to maintain the great circle. The finished flight path would appear as a jagged saw tooth line.
![](https://www.sharpgis.net/image.axd?picture=StraightLines_Spheric.jpg)
![](https://i0.wp.com/aerosavvy.com/wp-content/uploads/2014/04/RollingGlobe-optimized.gif?resize=300%2C227&ssl=1)