BEIJING (Reuters) - Chinese authorities have told pilots who fly to Beijing they must be qualified to land their aircraft in the low visibility bought about by smog, state media said on Thursday, as the government tries to reduce flight delays due to pollution.

Beginning January 1, pilots flying from the country's 10 busiest airports into the Chinese capital must be qualified to use an instrument landing system on days when smog reduces visibility to around 400 meters (1,315 feet), the official China Daily said, citing China's civil aviation regulator.

"It is part of a series of measures the administration took recently to raise the flights' on-time performance," the newspaper quoted an unnamed aviation official as saying.

Despite investing billions of dollars in new airports and advanced Western-built aircraft, China suffers a chronic problem with flight delays, partly because of the country's often wildly-fluctuating weather and partly because the military tightly controls most of China's airspace.

Chinese media frequently reports fights, attacks on airport and airline workers and passengers storming aircraft in response to delays and the poor way they are handled, and the government has demanded airlines and airports address the issue.

In recent years, smog has added to the problem of delays, especially in Beijing but also in other parts of the country like cosmopolitan business hub Shanghai.

"Considering the recent smog and haze has bought numerous troubles to air transport in eastern and southern regions, it seems necessary for authorities to ask pilots to improve their landing capability in low visibility," the China Daily quoted Ouyang Jie, a professor at Civil Aviation University of China, as saying.

The report added that only a handful of Chinese airports have the instrument landing systems required for aircraft to land in poor visibility.

Air quality in cities is of increasing concern to China's stability-obsessed leaders, anxious to douse potential unrest as a more affluent urban population turns against a growth-at-all-costs economic model that has poisoned much of the country's air, water and soil.

China's state media came under fire this week for arguing the smog had a benefit, that it would hinder the use of guided missiles and could help Chinese people's sense of humor.

(Reporting by Ben Blanchard; Editing by Michael Perry)