CORRECTED - GM rejoins S&P 500 four years after U.S. bailout

(Corrects headline and first three paragraphs to delete reference to AIG rejoining the S&P 500 index; AIG is joining the S&P 100 but never left the S&P 500)

DETROIT (Reuters) - General Motors Co will rejoin the S&P 500 index this week, marking a key milestone in the recovery of a company that needed billions of dollars to stay afloat during the financial crisis.

GM will return to the S&P 500 after the stock market closes on Thursday, the S&P Dow Jones Indices said on Monday. At the same time, American International Group Inc will join the S&P 100 index.

The move represents a symbolic victory for GM, which has taken steps to overhaul its operations and return to viability since its near-collapse in 2009.

Companies in this index are considered leaders in their industry, the S&P said on its website. Returning to the index will help boost shares, particularly important in the case of GM, which is still partially owned by the U.S. government.

AIG received $182 billion in U.S. funds, while GM took $50 billion during the economic recession in 2008 and 2009. The bailouts were highly controversial, but government officials said they were necessary to stabilize the weak U.S. economy.

In December, the U.S. Treasury Department announced it was selling its remaining stake in AIG. Taxpayers made a profit on the AIG bailout, a once unthinkable outcome.

Later that month, the U.S. Treasury said it would exit GM by early 2014. But unlike AIG's case, the U.S. government is likely to lose billions of dollars on GM.

GM will replace H. J. Heinz Co in the S&P 500 and 100 indexes, while AIG will replace Baker Hughes Inc in the S&P 100 index, S&P said.

(Reporting by Deepa Seetharaman; Editing by Stephen Coates)