contrails

This might be slightly off topic, but the APOD picture today made me
think of it. Has anyone noticed contrails toward the horizon that
appear to go almost vertically downward, as if we're seeing around the
curvature of the earth's atmosphere being 40,000 feet below the path
of the airplane? Is that what's happening? What I'm picturing is
concentric spheres with their surfaces 40,000 feet apart (the larger
one 80,000 feet larger in diameter than the sphere inside it) and
we're on the surface of the smaller one looking up and tracing a line
drawn on the surface of the larger one.

Now for the really off topic question...When I flew from Shannon,
Ireland to New York City, we flew over what looked like a glacier.
Does the curved flight path from Ireland take you over Greenland or
Iceland?

Clear Skies,
Paul Murphy