...S&P Global Ratings assigned its 'A-' long-term rating to Miami-Dade County's approximately $290.2 million series 2020A aviation revenue refunding bonds (non-AMT) and approximately $122.5 million taxable series 2020B aviation revenue refunding bonds issued for Miami International Airport (MIA). The outlook is negative. Securing debt service on the bonds is net revenue of the county's port authority properties, which substantially consist of MIA, three general aviation airports, and one training airport. MIA generates the majority of net revenue. Proceeds from the transaction will refund bonds outstanding to lower overall debt service requirements with estimated savings of about 16.8% of the refunded par amount. Although the refunding structure condenses savings into fiscal years 2021 and 2022, no dissavings occur in any year and there is no extension of the original final maturity dates on the refunded bonds. At Sept. 30, 2020, and following the refunding transactions, MIA had about $5.5...