Three investment groups have submitted bids of less than $5 billion to acquire International Lease Finance, the aircraft lessor owned by American International Group ( AIG), a report says. One consortium was led by Thomas H. Lee Partners and Carlyle Group, while Onex and Greenbriar Equity Group headlined a second group. The third bidder's identity couldn't be determined, the Financial Times reports, citing people close to the situation. International Lease Finance's book value is about $7.6 billion, the Financial Times notes. The sale of the unit would represent AIG's biggest since it was first bailed out by the U.S. government in September. AIG is likely to negotiate with the three groups for several weeks before presenting the winning bid to the New York Federal Reserve and U.S. Treasury, which hold a stake of about 80% in the insurer, the Financial Times reports. AIG has received about $180 billion from the U.S. government to help the insurer avert a collapse. AIG, International Lease and the bidders declined to comment for the Financial Times.