NEW YORK (S&P Global Ratings) July 21, 2017--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. "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," said S&P Global Ratings credit analyst Joseph Pezzimenti. Bond proceeds, together with other legally available funds, will refund some aviation revenue bonds outstanding