the shortest air route is a great circle
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Great Circle Route
The shortest route between two points on the surface of a planet, when routes are limited to the planet's surface, is the arc of the great circle that connects the two points. The shortest route between two points anywhere, without regard to intervening matter or energy preventing the route from being followed, is always the line connecting the two points.
If you mean by the words "direct route" the shortest distance between two places, distances between two places are shortest at the equator, because of the shape of the planet. If you mean which direction should be traveled to minimize distance, the route taken should be as straight a line as possible.
Because that location is the lowest, shortest route between oceans.
straight line
The shortest route is on I-90 W.
We are an aircraft delivery company and have often reviewed the shortest flying route to Hawaii. The shortest direct route between two airports is Monterey, California to Hilo Hawaii at 2012 Nautical Miles. Fred Sorenson Flight Contract Services, Inc.
about 1900 miles
2.712 km on the shortest public road route
The shortest route between South America and Africa would have you leaving from the nation of Brazil. Brazil remained a Portuguese colony until 1808.
the shortest route between the two is a great circle path that passes the two end destinations.