Forty years ago, in an entry level job, a coworker and I spoke about our nationwide call-in clients in airport codes. She was a former flight attendant. I was a not-as-heavily-traveled-as-I-wanted-to-be wannabe. I'm much better traveled now. I still think about cities and destinations in airport codes, but now more of those codes may be ICAO codes instead of the more common IATA codes. For example, Princess Juliana airport to me is TNCM when I'm tracking flights, but SXM when I'm booking flights. Likewise, depending on what I'm doing, the St Barth airport may be either TFFJ or SBH.