During inspiration the main current of airflow in a normal nasal cavity is through -
Nose is the natural pathway for breathing.
During quiet respiration:

Inspiratory air current passes through middle part of nose between the turbinates and nasal septum.
Very little air passes through inferior meatus or olfactory region of nose. Therefore, weak odorous substances have to be sniffed before they can reach olfactory, area.
During expiratorn, air current follows the same course as during inspiration, but the entire air current is not expelled directly through the nares.
Friction offered at limen nasi converts it into eddies under cover of inferior and middle turbinates and thus sinuses are ventilated during expiration.

Ref. Dhingra 5/e, p 155; 6/e, p 140
Middle part of the cavity in middle meatus in a parabolic curve
Lower part of the cavity in the inferior meatus in a parabolic curve
Superior part of the cavity in the superior meatus
Through olfactory area