Airline pilots are educated to understand that Earth is a sphere and depend on the knowledge to do their job. They have plenty of opportunities to observe Earth’s curvature, either visually or using the airplane’s instruments. They are also aware that there are people out there that somehow believe in flat Earth, and some of the pilots even actively debunk flat Earth in their spare time.
Flat-Earthers asked some of the pilots if Earth is flat and rudely recorded the conversation. Then, they would brag online if they can get the pilots to “admit” in camera that Earth is flat. In reality, these pilots are professionals on the job and aware of the erratic behavior of the flat-Earthers. They were just trying to get rid of these people as quickly as possible without making a scene.