The Civil Aviation Administration of China said Dec. 12 that it had concerns about the safety of Boeing Co.'s 737 MAX airplane, after the U.S. Federal Aviation Administration chief Steve Dickson said the model was unlikely to resume flights before the end of 2019, Reuters reported.

China moved first to ground the airplane in March following two fatal crashes in about five months, before setting up its own task force to evaluate Boeing's design changes in April.

"The CAAC has raised our important concerns on areas such as system reliability and safety assessment," spokesman Liu Lusong told reporters, reiterating that the model must be recertified and that pilots will be required to complete training before 737 MAX could resume flights in China.

China, which had the most 737 MAX planes in service prior to its grounding, did not specify when the aircraft would be cleared to fly in the country, Reuters reported.