The program to develop the Comac C919 is likely to miss its target for first flight in 2014, even though it is not showing signs of severe delays, such as those that afflicted recent Western programs, sources say.

When the development program reached its halfway mark this year, it had exhausted the spare time built into its timetable. “When I look at the schedule from here, it is only just possible to make the first flight on time,” says one source familiar with the progress of the aircraft’s systems development. “There is no room for any more delays.”

As for the chance of the first prototype flying on time, that source says, “I would say it is much less than 50%.” If the first flight is late, certification and first delivery will be late as well.

A year ago, there was the risk that the program would be brought to a halt by slow progress in Comac’s earlier program, the ARJ21 regional jet, which the Civil Aviation Administration of China (CAAC) and the FAA have been using as a test of the Chinese authority’s ability to certify the airworthiness of commercial aircraft to Western standards. The FAA last year questioned whether the CAAC should support detail design of the C919 before it had completed the ARJ21.

Now, a source says, the FAA has relaxed its stance. It says that if the CAAC follows the same procedures for the C919 as used when overseeing ARJ21 detail design, then that work should be valid. The underlying assumption is that the regional jet’s certification work meets FAA standards. The C919 is now fully in the detail design phase, with CAAC support.

Even optimistic industry officials are not comfortable with Comac’s flight-test schedule. The C919 surely will not spend six years in flight tests, like the ARJ21, but one source believes the plan to produce the five flight-test aircraft at two-month intervals is unrealistic.

“The structure will certainly be ready for the first flight,” that source says, noting that Comac even after more than four years of development still is spending money on alternative structural systems, in case its primary design proves unviable.

The Chinese manufacturer was not available for comment.

The key design target of the C919 is to deliver a 10% reduction in operating costs, compared with current-production Boeing 737s and Airbus A320s, although those aircraft are being updated with new, more efficient engines. A common view among people involved in the C919 program is that Comac will do quite well if it can match the operational performance of the updated Western narrowbodies, but even then it will have the challenge of persuading customers that the aircraft will be reliable and will be supported in service.