Airline code RT?
 

As you will see, this question could as easily go in the SEAsia thread. Mods, please feel free to put it wherever it you like.

As far as I can tell, RT has been assigned to two [granted, somewhat obscure] carriers. RAK Airways, a scheduled, if sporadically so, carrier headquartered at RKT, and Skyview Airways Co., Ltd., d/b/a R Airlines, a charter carrier headquartered at DMK.

This can't be right. Anyone have any additional info?

According to both Wikipedia and airlinecodes.co.uk, RT is Rak Airways, and RK is R Airlines.

Yup, you're right. And now I can't find the page which made me think that there was a duplication. OK, sorry for wasting everyone's time.

RAK Airways is officially done and dusted now, so RT will be available for reassignment at the end of the year.

My understanding was that IATA got around the limitation of two-letter codes by allowing duplication only with geographical separation (OM was for a time attributed to both Mongolian and Monarch) then encouraging use of three-letter codes.

There are a number of factors that go into controlled duplicate assignment, including geographical separation, type of operation (cargo/passenger, scheduled/charter, etc...) but in the end, basic common sense usually prevails. I've successfully petitioned IATA for a controlled duplicate alpha-alpha code assignment as recently as 2012 and it was a straightforward process if you have the proper arguments to make.