Why the ‘O’ in San Francisco’s Airport Code, SFO?

<p>Why the "O" in SFO? And why is one of Chicago's airports coded ORD? And IAD for Dulles?</p><p><br></p><p>Reported by Jessica Placzek. Bay Curious is Olivia Allen-Price, Vinnee Tong, Paul Lancour, Suzie Racho, Penny Nelson and Julia McEvoy. Theme music by Pat Mesiti-Miller.</p><p>Ask us a question at BayCurious.org.</p><p>Follow Olivia Allen-Price on Twitter @oallenprice.</p>