The whole effectiveness of aircraft such as the B-2 and F-117 Stealth-Fighter is to clear out the SAMs and anti-aircraft defences so that conventional aircraft can operate more effectively. So far as I am aware the first few missions of the Iraqi Freedom campaign involved B-2s and F-117s scouting and destroying Iraqi SAM and aircraft defence sites so that the other aircraft could come in and do their work. These stealth aircraft are necessary to undertake work for protecting conventional aircraft that come in later.