that man is a ignorant liar
I've been on a number of flights myself and I've never seen curvature to the earth.
in Alaska there is a time period where it is dark for days on end. this has been proven because of the earths axis and the roundness of the earth. what are your opinions on this subject?
The radius of the sun's orbit around the Earth's axis symmetry varies throughout the year, being smallest when summer is in the northern annulus and largest when it is summer in the southern annulus.

When the sun is in its Southern Annulus the North Pole and parts of Alaska are in perpetual night.
When the sun is in its Northern Annulus the North Pole and parts of Alaska experience a perpetual day