The Comac ARJ21 regional jet project has been delayed again, with the aircraft now due to enter service in April or May 2015, eight years later than scheduled early in the program and 13 years after development began.

The first operator, Comac subsidiary Chengdu Airlines, will receive its initial unit from the manufacturer late this year or early next year, says Luo Ning, the carrier’s deputy general manager. After that, further preparations will be made before operations begin in April or May, Luo tells local media.

The ARJ21 has probably been delayed more times than even Comac can count. As recently as last August, the first delivery was due in June of this year. When full-scale development began in April 2002, the first delivery was due in 2006, although within weeks that target had been shifted to 2007.

Among the more recent problems, an unexpectedly high landing weight forced a redesign of the landing gear by supplier Liebherr. Before that, the ARJ21’s mainplane failed its ultimate load test and needed redesign.

Comac says it completed the first two ARJ21s for Chengdu Airlines in late December. Aircraft MSN 103, meanwhile, has completed cold weather tests in Inner Mongolia, with temperatures as low as minus 43.2C. That included operation of the ram-air turbine in those conditions. Tests with unit MSN 104 to confirm the ARJ21’s high-speed characteristics are also complete, says Comac. Those tests included determination of out-of-trim characteristics and buffeting properties, including flight at the buffet boundary.

The ARJ21 is designed to seat 90 in an all-economy arrangement.

Meanwhile, structural manufacturing is proceeding for Comac’s second type, the 158-seat C919 mainline airliner, with Avic’s Chengdu civil aircraft plant completing the first major assembly for the nose of the first prototype. The assembly, including the windscreen frame, is the structure enclosing the cockpit, bounded by the forward bulkhead and the floor. The C919, so far delayed by only about a year, is due to make its first flight next year. The first delivery probably cannot be made before 2017, compared with the original target of 2016.

Delays are detracting from the ARJ21’s competitiveness, which in any case has been in doubt because of Comac’s inexperience in development. While the manufacturer, a state agency registered as a company, has been challenged in integrating the ARJ21’s systems to extract optimal performance, the technology that it has been working with has been aging.

The problem is particularly evident in propulsion. The aircraft was launched with what was then a quite new engine, the General Electric CF34-10, used by the similarly sized Embraer E Jet, which had entered development three years earlier. But by 2008 Mitsubishi Aircraft had chosen the more fuel-efficient Pratt & Whitney PW1217G geared turbofan for its MRJ, also close to the ARJ21 in size. A year ago Embraer decided to drop the CF34-10 and switch to the Pratt & Whitney engine for an extensively revamped E Jet design.

Luo’s prediction of entry into service next year presupposes that the ARJ21 will finally be certified. The Civil Aviation Administration of China (CAAC) is overseeing the airworthiness certification process with guidance from the FAA. If the CAAC handles the ARJ21’s application to the satisfaction of the FAA, the U.S. agency will recognize Chinese airworthiness certificates for later projects, possibly including the C919. To achieve that recognition, the CAAC need not certify the ARJ21 as airworthy, however. A proper process resulting in rejection of Comac’s application for certification would also suffice.