Final assembly of the first flight-test Mitsubishi Regional Jet begun today, two months after programme delays were confirmed.

The work is being undertaken at Mitsubishi Heavy Industries' "aerospace systems works" in Nagoya, the aircraft's mid-fuselage having been transferred from the Japanese manufacturer's Tobishima facility, located some 30km away, on 13 October.

In August, Mitsubishi Aircraft delayed the MRJ's first flight by more than a year, to the second quarter of 2015, saying that design and certification had "taken greater resources than anticipated". First delivery was also pushed back, from the summer of 2015 to the second quarter of 2017. This was the second time the airframer had revised the schedule: in April 2012, it moved the first-flight target from that year's second quarter to the end of 2013.

Now, it says final assembly will "progressively advance as other sections of the fuselage, main wings and other structural components arrive, after which electrical wiring, hydraulic and other systems will be installed, followed by other necessary equipment".

As part of final assembly, the vertical and horizontal stabilisers – being built at MHI's Oye plant, also in Nagoya – will be integrated with the airframe, as will its Pratt & Whitney PW1200G geared turbofan engine.

There are 165 firm orders in the MRJ backlog. Launch customer All Nippon Airways accounts for 15 of these, while US-based SkyWest Airlines and Trans States Holdings have firmly committed to 100 and 50, respectively. Between them, the three MRJ customers hold a total of 160 options.