Originally, Crissy Field was considered ideal for air operations. However, wind and fog often made for poor flying conditions, construction of the Golden Gate Bridge threatened to make local flights more difficult, and the runway was too short for more heavily loaded aircraft. The Army also considered Crissy Field vulnerable to possible enemy ship attacks due to its location on the water's edge of the San Francisco Bay. In 1936, Hamilton Field opened in Marin County, and while Crissy Field ceased to be a first-line air base, air operations continued until the 1970s.