Different values of "we" going on here. "We" know how heavier-than-air flight works in the sense that it is known to science. "We" in the comments don't know, because most of us here have at most a Bachelor's in physics, and it takes more than that to really grok aerodynamics, but everyone (including me) can't resist the temptation to show off what partial knowledge they have from that undergrad fluid dynamics class.

The fact that the second "we" doesn't really know aerodynamics, and is going to waste man-days chasing its own half-understandings round in circles in the comments, doesn't contradict that fact that the first "we" does understand aerodynamics. Planes aren't staying in the sky by accident, nor even just by the survivorship of trial-and-error engineering.