In other words, a passenger flying on a Chinese airline experiences a flight delay in one of every three trips.

　　The data shows that the on-schedule rate exceeded 72 percent in January, the highest in the first six months and almost at the same level as a year ago.

　　But the rate declined in the following months with June suffering the worst slide as it dropped to below 60 percent.

　　中国飞机航班延误情况恶化

　　Gao Yuanyang with the aeronautics-focused Beihang University says many factors can affect the rate.

　　"Weather conditions, the management quality of an airline company, the scheduling of airport runway operations and airspace arrangements all play important roles. Sometimes, an unexpected small change is enough to spoil a well-designed flight plan."

　　Meanwhile, a notable increase in passenger flow and unchanged air route capacity are believed to contribute to massive delays.

　　Stats show that the monthly increase of air passenger flow in China exceeded 10 percent in the first half of the year.

　　The airports in Beijing, Shanghai and Guangzhou have to deal with at least 90 take-offs and landings per hour, while the average amount of traffic on the country's busiest air routes exceeds 11-hundred planes a day, nearly double that seen in Europe and America.

　　Gao Yuanyang says delays are inevitable in the face of such busy air traffic.

　　"There must be a certain distance between two landing planes. If the distance is not long enough, the latter one will be ordered to wait by circling around in the air. And if the arrival airport is too busy to receive any more flights, the departure airport will postpone the take-off of the plane."

　　Gao suggests that domestic air control authorities could expand air route capacity by allowing more aircrafts to fly in the same airspace but at different altitudes.

　　The CAAC also blames increasing extreme weather events this year for worsening flight delays.

　　The authority also revealed that it has received about 700 complaints about delays this year. Most complaints centered on getting stranded on board while waiting for take-off, slow information updates and unsatisfactory compensation for passengers.

　　For CRI, I'm Luo Wen.