The boundary layer mesh (prisms / hexas) is automatically adjusted via motion of its layers in order to meet specified wall resolution requirements. The wall criteria include the y+ values, a specified thickness of the first layer, etc. Grid quality is enforced during the mesh movement.
Aircraft - y+ Redistribution
The mesh in the wall regions adjusts the position of its layers based on the y+ values calculated on the aircraft surface. Notice the boundary layer mesh for the nose of the aircraft before and after the redistribution. The initial mesh produced a y+ value much higher than the desired value. After redistributing the mesh, the final y+ value was lowered to near the goal.