Abstract: A system for locking and unlocking an opening panel includes a mobile bolt and a mobile locking part adapted to cooperate with the bolt, the bolt adapted to occupy a first deployed position in which it is retained by the action of the locking part and a second deployed position in which it is no longer acted on by the locking part. The locking part is designed to occupy a locking position in which it retains the bolt in its first deployed position in the absence of external action on the part and to move from its locking position to an unlocking position by the action of an external force. The system includes a mobile counter-bolt adapted to be deployed and retracted on closing and opening the opening panel and to prevent the locking part returning to its locking position when the bolt is in its second deployed position.