(Yicai Global) Feb. 23 -- Chinese airlines were more efficient last year after transporting 552 million passengers and more than seven million tons of cargo and mail.

Passenger volumes leapt 13 percent on the year as airlines filled more seats, increasing the average passenger load factor by half a percentage point to 83.2 percent, data from the Civil Aviation Administration of China shows. The PLF is the number of passengers traveling on a plane compared with the number of seats available.

Chinese carriers struggle with punctuality and are becoming increasingly threatened by advances in high-speed rail technology. They had a punctuality rate of 66 percent over the first eight months of last year, with flights delayed by an average of 30 minutes.

The CAAC stepped up in September, demanding airports better manage flight volumes to make sure they leave on time, but insiders believe the issue is the nation's airspace management model. China permits civilian aircraft to operate in 20 percent of its total airspace, despite flight volumes rising by about 10 percent a year.

In terms of air freight, China's civil aviation sector turned over more than 108 million ton-kilometers of cargo in 2017, up 12.5 percent on the year. Internationally-shipped cargo grew faster but domestic routes shipped more, making up 64 percent of the total, CAAC data shows. Eastern China bore the brunt of the load, carrying more than half of the total cargo and passenger volumes.