NEW YORK -- American International Group Inc. ( AIG) says it will sell up to 90% of its airplane leasing unit International Lease Finance Corp. to an investor group led by Weng Xianding, chairman of New China Trust Co. Ltd., for approximately $5.28 billion.The investor group, which includes New China Trust, China Aviation Industrial Fund and P3 Investments Ltd., will acquire 80.1% of ILFC for approximately $4.23 billion, with an option for an additional 9.9% stake. AIG will keep at least 10% of the company. ILFC will remain based in Los Angeles. The agreement needs approval from U.S. and Chinese regulatory authorities. New York-based AIG has been selling off subsidiaries to raise money to pay back its $182 billion bailout from the government during the economic meltdown.