What upward momentum? The air starts out still, and infinitely wide
wing comes flying through it,

As the wing approaches, the air starts moving up, eagerly anticipating
the meeting. Called "upwash".

Well, then an infinite wing ought to have something that is not
called
downwash, but keeps Newton happy. Call it downflow, call it pressure
bounce.. but it's something.

Newton is happy. The high pressure air on the bottom of the airfoil
pushes on the airfoil, the airfoil pushes back

Anyway, I'm just the messenger. The idea that there is no net downward
momentum of infinite airfoils is stated in a number of aerodynamics
books.