Japan's Mitsubishi Heavy Industries' logo is pictured outside the company headquarters in Tokyo Thomson Reuters By Tim Kelly and Siva Govindasamy

TOKYO/SINGAPORE (Reuters) - Mitsubishi Aircraft will roll out Japan's first commercial jet in more than 50 years on Saturday, amid doubts its ambition to sell more than 2,000 of the planes can match reality in the market segment.

Developed for $1.9 billion by a subsidiary of Mitsubishi Heavy Industries that includes Toyota Corp as a shareholder, the $42 million regional jet, with just under 100 seats, is Japan's second bid at breaking into the commercial aircraft market.

The last attempt in the 1960s, which failed, was a 64-seat turboprop dubbed the YS-11. Only 182 planes were ever built.

Mitsubishi has so far won 191 firm orders from customers including U.S. regional groups Trans States Holdings and SkyWest Inc, and Japan Airlines Co Ltd.

That, say analysts, is below the several hundred planes it will need to sell to break even and far behind the number of orders it will need to overtake market leader, Brazil's Embraer SA.

That goal presents a "significant challenge," said Rob Morris, head of consultancy at aviation market specialist Ascend.

The MRJ's biggest selling point, Mitsubishi says, is the ability to burn 20 percent less fuel than aircraft of similar size thanks to new-generation engines from Pratt & Whitney, a subsidiary of United Technologies Corp.

The plane, however, is already three years late because of design and development problems allowing Embraer to catch up. For Mitsubishi, it means a sprint to complete flight tests before the first delivery in June 2017 to ANA Holdings Inc.

CHALLENGING NUMBERS

Mitsubishi, which is also challenging Canada's Bombardier Inc, estimates demand for 5,000 regional jets over the next 20 years of which it aims to capture a half. Ascend puts its prospects closer to a fifth and forecasts a market for 4,071 jets worth $128.3 billion by 2033.

Embraer will supply 2,489 of those and Mitsubishi 913, with Bombardier and newcomers from Russia and China making up the rest, according to the Ascend Flightglobal Fleet Forecast.

Mitsubishi's problem is Embraer's headstart of over 1,000 aircraft orders, along with an established reputation for financing, reliability and after-sales service, said Richard Aboulafia, vice president of analysis at consultancy Teal Group.

After the MRJ came into the picture, Embraer said it would upgrade its E-Jets with the same fuel efficient Pratt & Whitney engines under the name E2. These will be delivered from 2018 only a year after the delayed MRJ.

"The E-Jet E2 will produce economics every bit as competitive as the MRJ, despite the lack of clean-sheet design," said Morris.

Mitsubishi has a better chance of displacing Bombardier, which has bet big on developing its CSeries to break into the market for 150-seat aircraft at the expense of its CRJ regional jets, said Aboulafia.

INDUSTRY AID

The MRJ's biggest success could be helping Japanese industry win component supply deals because it will prove to Boeing Co and other manufacturers like Airbus Group NV that Japan is capable of taking on more work. Doing so could help make up for less work building military aircraft.

Skills acquired on the YS-11 program helped Mitsubishi Heavy and other companies forge ties with Boeing.

They have a major work-share on the U.S. plane maker's 777 and 767 aircraft and build 35 percent of the carbon composite 787 Dreamliner. That work employs 22,000 people or two-fifths of Japan's aerospace engineers.

A government official overseeing Japan's aerospace business who spoke to Reuters likened the MRJ project to a 1,000-year-old Shinto renewal rite at the Ise Grand Shrine in central Japan near to Mitsubishi's MRJ plant. Shrine buildings are toppled and rebuilt every twenty years to pass on traditional building skills young carpenters.

"A regional jet won't be nearly as important, in terms of profits and technology development, as Japan's hugely important role as an aerostructures provider, particularly to Boeing, " said Aboulafia.

(Editing by Christopher Cushing)