S&P Global Ratings has assigned its 'A' long-term rating to Miami-Dade County, Fla.'s pro forma $654.6 million series 2017BCD aviation revenue refunding bonds issued for Miami International Airport (MIA). At the same time, S&P Global Ratings affirmed its 'A' rating on the county's aviation revenue bonds issued for MIA. The outlook is stable. Bond proceeds, together with other legally available funds, will refund some aviation revenue bonds outstanding for debt service savings without extending maturities. The rating reflects our assessment of a large connecting hub airport with a niche market dominance that has produced steady financial results despite having a high debt load, additional debt needs, and a high airline cost structure. Key credit strengths, in our opinion, include: The