can commercial airline pilots see the curvature of earth?

(a) No

(b) All airline pilots are commercial by definition and there is no such thing as a non-commercial airline pilot, so in future, just say "airline pilot".

yes

Yes and the passengers

No. Seeing the curvature of the Earth is a common misconception and a total fallacy unless you're so high you can see the edge of the planet.

Think about it. Look at a big ball and imagine you're just above the surface of it. You can see the horizon as a circle, but that horizon is a straight line because it is the same distance from you all the way round.

The fact that there is a horizon is because the Earth is a sphere (or very close to it) and it curves AWAY from you, but you cannot observe the actual curvature.

Absolutely.

Anybody who cares to look can see the curvature of the earth, even from the ground.

Find some flat level ground or better still look out to sea. Where the ground meets the sky that's called the horizon and is caused by the curvature of the earth.

Yes. Even from a light plane a few thousand feet AGL the horizon has a slight curve, but you need to be in an area where it is not obscured by the terrain or weather.

For example, flying over the coastline on a clear day you can see the curve of the horizon on the ocean, but often it's obscured by haze. I learned to fly in the Midwest of the US, and the curve was often visible.