Last December, the Air Force said that proprietary data rights justified a sole source, $100 million, follow-on contract to Northrop Grumman [NOC] for development of its Stand-in Attack Weapon (SiAW), but now the service is looking for alternatives. The stand-in strike division of the Air Force Life Cycle Management Center's (AFLCMC) armaments directorate said in a Wednesday business notice that the division is conducting market research "to identify potential sources capable of providing a SiAW equivalent missile system which consists…