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Airplane's shortest route

  1. Apr 4, 2008 #1
    Assuming that a plane, for practical reasons, needs to climb, then descend...

    If an airplane wanted to take the ABSOLUTE shortest distance from JFK to LAX, what typically needs to taken into consideration? Specifically, would you need to calculate simply the rotation of the Earth around its axis? Or would you also need to calculate in (as minute as it may be) the changing position of the Earth through space during the flight's time? If the latter, do the airlines typically get this detailed in their calculations?

    Also, when flying, are you still a part of a "closed system" due to the Earth's gravity?

    Finally, if you have any online sources of these calculations, that would be appreciated.

    Our office got a little noisy during this debate.

    Thanks very much in advance,
  2. jcsd
  3. Apr 4, 2008 #2


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    There is no preferred frame of reference - absolute is ambiguous.
  4. Apr 4, 2008 #3


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    The distance flown will vary only with the altitude, which is determined by air traffic control rather than the airlines.
  5. Apr 4, 2008 #4


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    The shortest distance is the great circle route. Earth's rotation or motion through space is irrelevant.
  6. Apr 4, 2008 #5


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    Yep, the shortest possible distance (without tunneling through the earth) is a great circle, at an altitude so low the plane is grazing the terrain. It's not very practical, though...

    - Warren
  7. Apr 4, 2008 #6


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    If you take into account the climb to altitude and decent from altitude, the shortest route will be the one that takes the shallowest climb and dive.

    Your second question actually holds the key to understanding this. Yes, you are part of a "closed system," so to speak. But this is not due to gravity. Rather, it results from the fact that you are flying through the Earth's atmosphere, which is essentially a part of the surface. It is also this fact which makes your question about "absolute" shortest distance impossible to answer. If the aircraft can climb to a higher altitude and find a tailwind going in the same direction, then the additional climb will make the distance traveled greater compared to an observer on the ground. But this route would be shorter in terms of the number of yards of air through which the aircraft passes.

    However, on a day when all of the air at every altitude is "still" (from the perspective of an observer on the ground), then the Earth's rotation on its axis and progression through orbit, the Sun's progress through the Galaxy, and the Galaxy's progress through space are all irrelevant, and the shortest path by ground is identical with the shortest path by air (except for the difference in altitude, of course).
    Last edited: Apr 4, 2008
  8. Apr 4, 2008 #7


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    And doesn't explalin why they will still route you through Denver and Dallas-Ft Worth!

    In my spherical trig class ( now after years of therapy a distant memory) there was always a question about the location of the northern most point on a great circle route from London to NY. the question was a certainty so we all prepared the answer in advance = somewhere in Greenland.
    Then somebody went to far and looked it up wrote in the exam = this is the small hamlet of Nowherefjord, population 36, main industry sheep painting (or whatever). The question never came up again.
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