Plenty of airports worldwide continue to use old airport IATA codes long after the airport changes name (e.g., BOM for Bombay, now Mumbai in India). These codes even apply to some important railway stations (e.g., London’s Paddington station has the code QQP while York station has QQY). But what about the airports in the United States with obscure airport codes and how do airports get their three-letter IATA codes?