Thermoplastic composites offer many opportunities for aeronautics. Among them is the possibility of overmolding composite parts to obtain finished “netshape” parts in medium series. This paper presents the complexity of the manufacturing method and the manufacturing defects that may occur in some grid-stiffened overmolded parts using aeronautic thermoplastics. The results of impact tests up to 15 J carried out at various locations of the plates and the grid show that, due to manufacturing defects at the overmolded grid/plate interface, very significant delaminations can be observed.