Complex sentence: The land was leased from Ogden L. Mills who had leased it from his grandfather Darius O. Mills, and was named Mills Field Municipal Airport until 1931 when it became San Francisco Municipal Airport.
Split into simpler sentences: The land was leased from Ogden L. Mills who had leased it from his grandfather Darius O. Mills. It was named Mills Field Municipal Airport until 1931, when it became San Francisco Municipal Airport.