(FORTUNE Magazine) - On March 16, three years to the day after the U.S. invaded Iraq, U.S. aircraft prepare for Operation Swarmer, the largest air offensive since the initial assault. The cost of the war, of course, has long since moved beyond the $50 billion figure Defense Secretary Donald Rumsfeld estimated in early 2003. Congress has approved roughly $301 billion for military operations in Iraq since the war's start; the Congressional Budget Office projects additional costs of at least $266 billion, assuming it takes a decade to wind things down. As for indirect costs (such as veterans' medical payments and the effect on oil prices), Columbia University economics professor Joseph Stiglitz asserts the full bill could be as high as $2.2 trillion.