Shares of Boeing are higher in U.S. premarket trading Thursday after China's aviation authority issued an airworthiness directive on the 737 MAX, and the planemaker's engine supplier provided a positive outlook. 

After more than two and a half years, the 737 MAX is on track to return to service in China, according to Reuters, citing a report from the Civil Aviation Administration of China (CAAC). The airworthiness directive instructs carriers on the changes required before the plane can return to service, although there was no timeframe on when the 737 MAX will return to the skies.