COMAC (Shanghai Pudong) has encountered multiple issues during the certification of its C919 and completed only 20% of its planned certification flight hours by December 2019, Reuters has reported citing sources related to the manufacturer.

The Chinese narrowbody made its first flight in May 2017. While the manufacturer has been secretive about the C919's type certification progress and planned timeline for deliveries, COMAC representatives, as well as the Chinese government, have previously spoken of achieving a type certificate by the end of 2020 or in 2021. However, given these delays, the timeline looks uncertain.

According to the sources, one of the problems pertains to erroneous calculations of wing loads related to the LEAP-1C engine, which has required a redesign of the engine and its shells. COMAC has yet to finalise the new design and provide new details to CFM International.

COMAC also discovered horizontal stabiliser cracks and engine gearbox cracks during the test. The former has already been resolved, while the latter has not yet, the sources said.

The manufacturer has so far received tentative orders for 815 C919s, almost all of them from Chinese airlines and lessors.

The type certification drive includes six testbed aircraft.