The serious answer for 1-alphabetical booking codes is probably hysterical raisins of the airline IT systems and IATA. This also applies to the 6-alphanumeric booking references and to fare basis, not to mention flight numbers and to our FT-beloved airport codes, airlines codes and cabin codes.

But who cares about booking codes now that we have ticket types! Ah, if only all OTAs showed the whole fare basis... so far I found only Kaleva/CWT and TravelLink.

So what's your interpretation of my personal favorite RVAFI2? :-)