The necessity to increase collaboration in nowadays supply chains is emphasized both by academics and practitioners, but most of the supply chains are still managed through cascades of classical MRP/MRP2 systems. Interviews in the aeronautical sector have shown us the existence of many hidden practices aiming at satisfying local constraints which would be better addressed through collaborative processes. We suggest in this communication to define a "collaborative MRP" which would not only provide a better global performance than purely local planning, but take into account the autonomy of the involved partners which is not always respected by centralized pproaches using APS (Advanced Planning Systems).