The Civil Aviation Administration of China said on Thursday that all safety concerns must be resolved before the Boeing 737 Max planes resume operation.

Gu Xiaohong, deputy director of the administration's general affairs department, said the administration has received notification from the Federal Aviation Administration of the United States that some Boeing 737 planes, including the now grounded Boeing 737 Max, may have defective parts in their wings.

The US aviation regulator issued a statement on Sunday warning that some wing components that provide greater lift during takeoff and landing, known as leading edge slat tracks, "may not meet all applicable regulatory requirements for strength and durability".

"The affected parts may be susceptible to premature failure or cracks resulting from the improper manufacturing process," the FAA said.

Checks would need to be carried out on 179 of the aircraft worldwide, as well as 133 older models called 737 NG to identify where the suspect parts had been installed, Boeing said.

The CAAC asked domestic airliners on Tuesday to check, remove and replace the parts if their 737 NG aircraft are affected, Gu said.

The administration is closely following the measures taken by the FAA and Boeing regarding the 737 Max aircraft, he said, adding that all safety issues must be resolved before the aircraft can resume service.

The Max jet has been grounded since March following two deadly crashes that have been linked to a separate concern about a piece of software in the plane.

The administration also said frequent rains and thunderstorms in May have caused more delays and flight cancellations.

A total of 10,320 flights were delayed and more than 3,000 canceled in cities including Beijing, Qingdao, Shanghai and Nanjing in May, said Sun Shaohua, deputy director of the administration's operation monitoring center.

With the peak summer travel season around the corner and increasing rainfall and extreme weather, there will be more pressure in the coming months to ensure normal flight operation, he said.

Airports, airliners and air traffic control authorities will strengthen cooperation to ensure normal flight operation during the storm season, including better sharing of information and data, more accuracy in meteorological reporting and more scientific flight schedules, Sun added.