Boeing Co will serve as consultant to Mitsubishi Heavy Industries for its mid-sized regional jet - the first "made in Japan" passenger aircraft in three decades, the Japanese machinery maker said on Sep. 4.

Mitsubishi has been a longtime partner with the U.S. aircraft maker, supplying the wing box for Boeing's 787 and other aircraft.

Boeing signed a deal to advise Mitsubishi on aircraft development, sales and customer support for the planned twin-engine Mitsubishi Regional Jet, or MRJ, that seats about 70 to 90 people.

Terms of the deal weren't disclosed. Mitsubishi said the agreement allows the Japanese company to gain from Boeing's expertise in the commercial airline business. The deal is not a surprise as Boeing officials have repeatedly expressed their willingness to support Mitsubishi's jet project.

The Mitsubishi Regional Jet is set to be a lightweight carbon-fiber composite plane designed to consume about 20 percent less fuel than comparable aircraft, according to Mitsubishi.

Japanese carrier All Nippon Airways (ANA) has placed the first orders for delivery from 2013.

Mitsubishi's mid-sized jet would face tough competition from Bombardier Inc of Canada, Brazil's Embraer SA and companies in China and Russia.

Demand for smaller jets is expected to rise over the next 20 years in regional markets. Mitsubishi has said its main target markets are North America, Europe and Japan.

Mitsubishi's jet will be Japan's first nationally funded, domestically manufactured passenger aircraft project since the YS-11, a turboprop airplane that was discontinued in 1973.

Mitsubishi - part of a major Japanese conglomerate that includes an automaker, electronics maker and trading company - has chosen Pratt & Whitney, a unit of United Technologies Corp, as the MRJ's engine supplier.