So, my friend and I got into an argument regarding the flight trajectory of a plane. He said that for half the journey the plane is ascending and for the rest, it is descending and hence making a parabolic curve. I argued that it ascends and then stays at the same altitude for the journey before descending to make a trapezoidal curve. After some contemplation, I think that both of us are right just that the baseline reference is different where he took it as a straight line between the two places without the curvature of the earth and hence it would make it parabolic while I took the trapezoidal curve by accounting the curvature of the earth.
We can also say it is from a different of view with him being in space while I am running on the ground to measure the altitude.
So, can someone clarify and tell who is right and whether what I think is correct or not?
It would be helpful if someone can actually plot the two graphs. Thank you.