and the answer is ... linked PNRs
IATA is mandating a very simple solution for the >16 segment problem: all IATA airlines must support linked PNRs by mid-2008. Many do now already; even AA has had this capability for years (but most Aagents are unfamiliar with it). The ticket can be arbitrarily long, split into 16 segment PNRs. This also allows for unlimited open jaws, if desired, as well as handling most other restrictions. And the ticket pieces can clear independently, so none of the back-end processes have to change, making this a fairly bullet-proof solution. So now you know why the airlines have mainly ignored this "problem", as it is a non-issue (or rather, already solved). Does make for good fodder for FT threads, I suppose.