Controllers are thoroughly versed in phonetics, that is words used in place of discrete letters so as to avoid confusion. For example, “s” sounds very much like “f” or “x” if you hear it on a not very expensive radio with a little static mixed in. Similarly “b” can sound like “d”, “t” or “v”. So, instead of “b” we say “bravo”—and there is a standard phonetic word for every letter of the alphabet. The phonetic alphabet used in ATC today is known as the ICAO (International Civil Aviation Organization), but it wasn't always the standard. In the early days of ATC, the old military WW II alphabet, Able, Baker, Charlie, Dog, was used.
Controllers, being the souls of brevity that they are, often substitute initials for words in their everyday language—RDO for regular day off, as an example. Sick Leave, similarly might have been said as Ess Ell, although two letter combos didn't really ring. So, folks used phonetics. And it started long ago—back in the Able, Baker, Charlie, Dog, days. Thus, Sick Leave became Sugar Lima, and it stuck—particularly as some of the letters in the ICAO alphabet are a little harsher to English speaking ears than the old alphabet (I just can't imagine saying “Sierra Lima”).
Anyway, one of the fellows in Chicago had a boat. A big boat. A boat that wouldn't fit on a trailer, but had to be moored at a slip. That brings to mind a whole additional dynamic given Great Lakes winters, but that's how he wanted to spend his off time. Which you would think would be on his RDOs, right? He named his boat Sugar Lima.
Last updated: 06 April 2009