Airline capacity has nudged back above 98 million with a further 680,000 seats added.
Cathay Pacific last topped the ranking in 2014.
The new deal, worth about USD 4.8 billion in total based on catalog price, came after a total of 100 new aircraft orders for the A320neo were placed by four Chinese airlines in July.
Capacity for the three months is 24% up on the same time series last year.
Biojet fuel, which cuts emissions of carbon dioxide by more than half over the whole life cycle, has gained momentum against the backdrop of carbon peak and carbon neutrality goals in the country in recent years.
The jet has not flown commercially in China since March 2019, when it was grounded after two fatal crashes.
The first C919 will be delivered to the first operator, China Eastern Airlines, before the end of the year.
Cathay has said it plans to hire an additional 4,000 staff to fill operational needs over the next 18 to 24 months as travel rebounds.
