Why nautical miles is used in aviation to measure distances ?
The ordinary mile is an arbitrary length of no particular significance in navigational calculations. However if I move one nautical mile along a meridian of longitude, the ‘north south’ lines on a map, my longitude changes by one minute of arc, which is one sixtieth of a degree. If I move along a great circle, the shortest distance between two points on the earth, one nautical mile again is one sixtieth of a degree. Over long distances this gives a link between distance and latitude and longitude. Over the short distances of weekend sailing or private pilot flying the link is rarely of any significance. One nautical mile is 1.15 statute miles, and a speed of one knot is one nautical mile per hour, or one degree along a meridian per hour. Big point is to make chart reading faster.
