<i>Large national airport.</i><p>I think there's something to be said for having more than one large airport, in competition with each other, in any large enough major metro area. Single-airport cities in my not-pluralizable-to-data experience have more problems with rental car shortages, weather, and traffic.<p>Perhaps it's just a question of number of airports per population and/or land area. About 1 per million people seems about right, even though the Bay Area falls shy of that.<p><a href="http://en.wikipedia.org/wiki/Table_of_United_States_Metropolitan_Statistical_Areas" rel="nofollow">http://en.wikipedia.org/wiki/Table_of_United_States_Metropol...</a>
<a href="http://en.wikipedia.org/wiki/List_of_the_100_largest_metropolitan_areas_in_Canada" rel="nofollow">http://en.wikipedia.org/wiki/List_of_the_100_largest_metropo...</a>
<a href="http://en.wikipedia.org/wiki/List_of_metropolitan_areas_by_population" rel="nofollow">http://en.wikipedia.org/wiki/List_of_metropolitan_areas_by_p...</a><p>Is there a convenient count of major and/or minor commercial airports for these areas?