The China Civil Airports Association (CCAA) said China Southern Airlines, the mainland's biggest in terms of fleet, network and passenger traffic, and 18 other carriers are not paying airport fees on time in an effort to bolster their cash flow.

Carriers owe a combined 1.4 billion yuan to 30 airports, the association said on December 27. Overdue fees for the quarter to the end of September include landing and take-off charges.

Carriers are withholding payments and using the money to compete for market share at home, the association said. Airlines made a combined 13.7 billion yuan in the first nine months, according to the General Administration of Civil Aviation of China (CAAC).