here are some examples from a thread that started 1.5 years ago
b99bebcaa150a44c6d36e2cff803325d0c729a70.jpeg (1680×1050) (flightsimulator.com)
84d978638c59d3ec90aef1701f95134db100af3b.jpeg (3393×1302) (flightsimulator.com)
b795223be7326a103413dac8a2994ded064b0cc2.jpeg (1680×1050) (flightsimulator.com)
but in principle all you have to do is go to the external camera, completely zoom out and move the camer around, you should see immediately the extent to which the image is spherically distorted except at the center as if you are inside a gigantic fishbowl.
The correct perspective is around zoom 70 but since the game does no allow to save the zoom to a fixed value, you’d have to fiddle with it every time.
within the cockpit you can set the default zoom level which already helps immensely, so we would need the option to do the same in external view, plus the ability to move the viepoint away from the plane (translation) instead of just zooming out.