Thrust reverser having an aerodynamic coupling for a front frame

A thrust reversal device for a turbojet engine nacelle comprising deflection grids and at least one cowl moveable relatively to at least one fixed structure including at least one at least partly peripheral front frame and equipped with means for connecting to a corresponding upstream portion, said at least one cowl being moveably mounted between a closing position in which the at least one cowl provides aerodynamic continuity of the turbojet engine nacelle and deactivates the deflection grids, an opening position in which the at least one cowl opens a passage in the turbojet engine nacelle and actuates the deflection grids, wherein the front frame has a deflection edge comprising an upstream extension forming a deformable flap to become an aerodynamic interface with the corresponding upstream portion to which is attached the front frame, and in that a portion of the at least one cowl is conformed so as to, in the closing position, interface with the corresponding upstream portion by forcing withdrawal of the deformable flap.