This week, anna.aero has collected 2011 traffic data for the top 20 airports in the USA, which reveals that between them passenger numbers grew by an estimated 2.5% in 2011. Of the top 20 airports, only two (Chicago O’Hare and Houston Bush) failed to record year-on-year growth, while only Miami recorded passenger growth of more than 6%. In terms of ranking, Houston Bush has dropped from seventh to tenth, as a result of which Las Vegas, San Francisco and Phoenix have all moved up a place. Further down, Seattle-Tacoma has overtaken Detroit for 16th place.