To get a photo of the curve of the horizon it helps if you are at a good altitude. Commercial AIrplanes are not the best option. But from the cockpit, you can see the curve better since you have a wider field of view. Also, the windshield is required not to add distortion.
VIew from the cockpit of an airplane:
Another from a cockpit:
The Concorde flew higher than other planes, here is a photo of the Concorde at cruising altitude with the horizon in view:
Passengers on the Concorde personally saw the curve of the horizon. DC Rainmaker took this photo:
Here is one from photographer Santiago Borja Photography in the cockpit of a plane: