The jury is still out on this one. If you ever want to start an argument between two aerodynamic engineers, ask them which force produces lift.

Personally, I subscribe to the theory that the Coanda effect deflects air downward, and Newton's third law of motion (for every action, there is an equal and opposite reaction) takes over.

Bernoulli's Principle has little to do with it. But that's my opinion, others may differ.