The rating on San Francisco Airport Commission's series A (AMT),series B (non-AMT), and C (taxable) commercial paper notes is based upon an irrevocable, direct-pay Letter of credit (LOC) provided by Societe Generale. The LOC provides full principal and interest coverage on the aggregate authorized amount of the notes (up to $300 million) issued and outstanding, and has a scheduled expiration date of April 12, 2002.