Mitsubishi Aircraft is set to announce a delay to the MRJ schedule amid undisclosed development difficulties.

Manufacturing of parts for the first prototype will begin this month or next month, says Hitoshi Iwasa, VP sales and marketing. On the current schedule, set in 2009, that prototype is supposed to fly in the second quarter of this year — which is clearly not possible for an aircraft whose parts have not entered production.

First delivery is due in the first quarter of 2014. Iwasa declines to say how long the possible delay could be. A decision will be made within a few months.

The company is doing all it can to recover its schedule, mobilizing its own resources, those of partners and suppliers, and also bringing in expertise from outside of the program. Mitsubishi Aircraft is not blaming a supplier or partner for the problem, and goes as far as saying that none has let it down.

“In some areas our development is going very smoothly and in other areas we are having difficulties. Some schedule impact will occur,” says Iwasa.

Mitsubishi Aircraft has encountered problems in development of the flight control system, says one industry executive not involved in the program. Since many parts from all across the airframe are about to go into production, it is evident that the developers’ problem is not in the structure. They did have a problem three years ago in integrating a composite wing with an aluminum body, but they solved that by making the wing aluminum—and announcing a three-month delay in delivery to launch customer All Nippon Airways. When the program schedule was drawn up, managers included contingency planning for unexpected delays, but not enough slack in the schedule.

The manufacturer says it is closely watching Embraer’s prospective update of the E-Jet, although it notes that a re-engined aircraft is not normally as efficient as one that was designed from the beginning for its current propulsion system.

The Embraer program could result in the two aircraft being more differentiated than they are now, because the Brazilian company is looking at adding a larger version to the family while perhaps not modernizing the smallest.

The largest E-Jet is already larger, and has more thrust than, the largest MRJ, the MRJ90. Although Mitsubishi Aircraft is looking at 100-seater, with extra frames for two more rows of four-abreast seating, that version would still not be as big as the E195, let alone Embraer’s contemplated further stretch. If Embraer does not modernize the E170, then the 78-seat MRJ70 will face less competition in that quiet part of the market.

On the other hand, a delay to the MRJ program will shorten the period in which Embraer had to compete with only its unmodernized aircraft.

If the contemplated MRJ100 goes ahead, it will have the same thrust rating as the MRJ90. The MRJ70 also uses the same engine, the Pratt & Whitney PW1217G, but with a lower thrust rating.

All Nippon has ordered 15 MRJs and Trans States Holdings of the U.S. has ordered 50. ANI Group Holdings, a Hong Kong subsidiary of lessor Aero Nusantara Indonesia, has signed a memorandum of understanding covering an intended order for five.

Mitsubishi Aircraft expects flight testing of the PW1217G to begin in the northern spring.

The company forecasts demand for 5,600 aircraft of 70 to 100 seats over the coming 20 years. Embraer expects airlines to buy 6,795 aircraft of 61 to 120 seats.