Is it guaranteed that the string isn't and won't be used for anything else than turning off airplane mode? We could easily imagine the same string used for wi-fi for instance.

If we're sure that it's only used in this specific context, what do you think of "Utiliser l'interrupteur matériel pour désactiver"?

At the moment it's used in the top right menu, in the menuitems displayed when you click on "Airplane mode           Enabled":

        if (hwAirplaneMode)
            this._offItem.label.text = _("Use hardware switch to turn off");
        else
            this._offItem.label.text = _("Turn Off");


and in the "wireless dialog", but also related to airplane mode:

        this._airplaneInactive = new St.Label({ style_class: 'nm-dialog-airplane-text',
                                                text: _("Use hardware switch to turn off") });

What I had in mind was more along the lines of "...pour le quitter" or "...pour en sortir", the key point being the pronoun, but that's not something that's usual, afaik.

I like your suggestions and I had something similar in mind without being able to come with something concrete. "… en sortir" sounds better. Can you take care of pushing the fix?

Thanks, done.