Eastern China was bracing for more flight delays on Tuesday, with reports saying Shanghai's main airports would be down to 25 per cent capacity after aviation authorities warned of busy airspace.
The Civil Aviation Administration of China (CAAC) last week confirmed military exercises are behind widespread flight delays and cancellations in the latter part of July.
CAAC's air traffic management bureau said east China will face "varying degrees" of flight delays from 2pm to 6pm, according to a posting on a website it operates.
Reports in state media, which quoted CAAC, said Shanghai's two main airports - Hongqiao and Pudong - would slash air traffic capacity by 75 per cent during the four-hour period, along with Zhengzhou in central China.
The Shanghai Daily said that implied more than 360 flights would be delayed in the commercial hub.
Shanghai's airport authority could not be reached for comment.
Eight small airports in eastern China would suspend all landings during the period, while nine others would stop some northbound flights from taking off, the Beijing News newspaper reported.
China's military controls much of the country's airspace - some estimates say as little as 20 per cent is reserved for civil flights. Industry officials say that results in longer flight times, less efficient routes and unaccountable delays.
China is holding military exercises across several provinces from July to October, state media have previously reported.
The civil aviation authority has classified the current flight delays with its highest alert, red, in a newly-established system which aims to better inform travellers.
The regular warnings are blue for normal, yellow for serious, orange for severe and red for especially severe, state media said.