An article in today's Daily Yomiuri talks about an ongoing pre-development design project between METI and Mitsubishi Heavy Industries to design a 70-90 passenger regional jet, to be powered by Rolls Royce engines. ("Heavy" would seem to be an unfortunate word to have in the name of a plane manufacturer, but never mind.) A go/no-go decision is expected next year, and it will debut in 2012. Tens of millions of dollars have been spent already, but that's nothing compared to full-blown development and manufacture of a passenger jet. It's expected that sales would have to be 350 planes to break even, and 600 to make a decent profit.
The plane's selling point is expected to be that it will be 20% more fuel efficient than similar planes from other manufacturers, but the article doesn't say how that's to be achieved. It also says that MHI wants to work with trading houses to arrange favorable financing for export.
Japan hasn't produced a full airliner of its own since the YS-11, which ended production in 1973 after production of 182 planes. I'm looking forward to someday flying on a Honda Jet, though.