Comac will miss a target to fly its C919 158-seat narrowbody airliner in 2014, industry sources familiar with the Chinese program tell Aviation Week.

The first flight is now scheduled for the second quarter of 2015, says one industry source with detailed knowledge of the program. According to the new plan, Comac will roll out the aircraft in December 2014, says the source, adding that the manufacturer is still aiming to achieve its target of a first delivery in 2016—but only just. The specific aim is now December of that year.

The first flight has been delayed by up to a year from a previous, unannounced target of June 2014.

Program managers had scheduled at least two years for flight testing. They now have about 18 months for testing, closer to the time allocated for flight tests by Western manufacturers.

The C919’s new schedule more closely matches the timetable for its engine. The CFM Leap-1C engine is due to be certified in June 2015, although the Civil Aviation Administration of China could permit C919 flight testing before the engine is certified.

The first Leap-1C should go into testing in the fall of this year, or at least no later than the fourth quarter.

Comac, a government agency registered as a company, made the decision to reschedule months ago, say three industry sources.

The delay is no surprise. The C919, launched in 2008, began to miss schedule targets as early as the supplier selection and contracting stage. One program manager later acknowledged that Comac simply was inexperienced in that process, despite having gone through it about six years earlier with its ARJ21 regional jet.

Industry sources close to the program remain skeptical about the new target; suppliers also are known to be expecting first deliveries in 2018, not 2016.

A strong sign that things were not going well emerged in April when it was revealed that Comac had switched the material for the center wing box, the structural heart of the aircraft, from carbon-fiber composite to aluminum.

Industry sources at the time said the change was made because the manufacturer saw too much risk in building the composite part. Another industry source now says that the problem was that the composite center wing box, built with foreign help, would have cost too much.

To some extent Comac was ready for the change, because early in its program it decided to develop aluminum alternatives to composite parts. Development of the aluminum center wing box should have been well advanced when the decision to use it was made.