Yann was not making a statement about deep nets' ability (or lack thereof) to fly a plane in a way that matches expert design.

He's making the point that the ML field's obsession with causal inference (and causal discovery) is overrated, precisely because our gold standards of interpretable, safety-critical systems (airplane flight) are based on Navier Stokes/CFD. Planes were made to fly based on empirical validation of these models, long before we gained a more detailed understanding of how causality (the equations and models themselves are time reversible, implying that they contain imperfect knowledge of causality)