Flight distance vs. shortest distance

Tiras25
Tiras25 used Ask the Experts™
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Stupid question, please see attached.  When measuring the actual shortest distance between SFO to Amsterdam is shows 5,425mi.  The airplane route shows longer 10k+ miles.   Why wouldn't the flight goes the shortest distance?  Or is it how the distance vs measurement shows on the map just for user's simplicity?  

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Get a world globe and attach the beginning and end point with a string.  Note the path as if it were on the map projection you're using.
It's called a Great Circle Route and *is* the Shortest distance - if the string is tight!  :-)

When measuring the actual shortest distance between SFO to Amsterdam is shows 5,425mi
.Where did you get your "shortest distance"?    Consider that it's nearly 4,000 miles from US coast to coast.  Then there's the Atlantic Ocean to cross, etc. etc.  So 5,425 SFO to Amsterdam???
Principal Software Engineer
Commented:
Looking at the "shortest route", most of it is over uninhabited areas, ocean and sub-Arctic lands.  If there were any trouble en route, the pilot would seldom be in emergency range of a major airport capable of landing a commercial jetliner and an emergency landing would be in territories unfriendly to urban humans.

Aside from that, I don't think that the mileage the map indicates over this route is correct.

The commercial route keeps the aircraft within emergency range of major airports in the U.S. and Canada until it goes feet-wet in Newfoundland.
The first question is "How did you get your shortest distance of 5425 mi?
The answer to YOUR question is that the airplane does not necessarily fly the shortest distance. Especially at the busy airports at the beginning and end, air congestion requires that a specific paths be used depending on time and traffic. In the US there are specific paths which much be used depending on circumstances.
The greatest variable in airplane path other than air traffic control likelihoods and local deviations is likely the jet stream.
On a flight like the one you're looking at, the selection of flight path can make the difference in flight time (over the ground speed) of an hour.  That's why west to east flight times are shorter than east to west.....
mccarlIT Business Systems Analyst / Software Developer
Top Expert 2015

Commented:
Another reason why a plane generally WON'T fly the "great circle" route (shortest distance) is that it is NOT a "constant bearing" route. Planes fly on a bearing, and why that bearing may change at certain points, in between those points you want the bearing to stay the same, so that pilots (and autopilots) can use their instruments to track that bearing.

Have a look at that "shortest distance" route. When projected on a map, it is curved. It starts out heading roughly north-east and finishes heading south-east, and gradually changes between the two heading throughout the entire route.

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