Jointly developing weapons carries considerable costs: decisions are arduous and work has to be shared out. Reconciling the needs of each can result in building countless variants, or in piling multiple requirements on a single aircraft. This happened to the A400M, which suffered a cost overrun of more than €11 billion. Germany wanted it to skim over treetops, Britain needed it to lift (now-scrapped) new armoured vehicles. Both Britain and France said it had to operate from rough airfields. One Airbus insider calls the A400M an eierlegende Wollmilchsau, or “egg-producing wool-milk-sow”.*Hilarious imagery, and timely in light of the Army's decision last week to cancel the original solicitation for Ground Combat Vehicle (GCV) proposals. Secretary Gates has made the point repeatedly that while industry is to blame for a great many ills of the acquisition and contracting process, the government has its own responsibility to ensure that requirements are well-defined, stable, and ultimately, satisfiable with a reasonable amount of risk.
* No need to parse the translation, Positroll and other German speakers, if it's not totally accurate. Those are the Economist's words, not mine!