In Hyperloop air bearings, the air escapes through the rear cross-sectional area of each ski, you know? Yes, there is a pressure differential, but the air comes out of the skis, crashes into the tube and then is accelerated to a certain speed below 760 mph/1,220 kph and escape. The air cannot escape through the front cross-sectional area because of the ski high speed and for the same reason they cannot escape through the lateral areas (well, there will be some minor leaks). That's Couette-Poiseuille flow.
So the mass flow is rhoAc
Where c is the speed the air is accelerated to, rho is the density, and A the rear cross-sectional area.
What do you think?