Plane sailing solves problems involving a single course and distance, difference of latitude, and departure, in which the Earth is regarded as a plane surface.
This method, therefore, provides solution for latitude of the point of arrival, but not for longitude. To calculate the longitude, the spherical sailings are necessary.
Plane sailing is not intended for distances of more than a few hundred miles.
Since the track is cutting all meridians at the same angle, Plane Sailing is also one of the methods of Rhumb Line Sailing. In a short distance, a rhumb line appears as straight line, but the track is actually a curve and, if extended, it will eventually spiral in on the North or South Pole. Because the unit of latitude is not the same as the unit of longitude, the difference of longitude has to be calculated to become departure, which is expressed as a latitude unit.