To improve the seal between a wing and a ventral fairing of an aircraft, an assembly includes an air seal system arranged in an opening, between the ventral fairing and the wing. The seal system includes a sealing blade, a first end of which presses against the wing, and a connecting device, on the ventral fairing, for a second blade end that is opposite the first end. The connecting device includes at least one first connecting layer, of which a first connecting face is secured to a first surface of the sealing blade, and of which a second face, opposite the first face, is secured to the ventral fairing, the first connecting layer being made of a material including an elastomer.