Passengers pack the waiting hall at Hongqiao Railway Station, which serves Shanghai Hongqiao International Airport, on Tuesday. Eastern China was bracing for more flight delays. (Johannes Eisele/AFP/Getty Images)

While passengers normally measure flight delays in terms of hours, in China it’s been two weeks of hell — and it only looks to be getting worse.

The delays and cancellations — the worse so far this year — began suddenly last week with hundreds of flights in Beijing and Shanghai affected with little explanation. Passengers spent days and nights decamped throughout terminals.

Then authorities announced Tuesday that the air traffic capacity at Shanghai airports would be cut down by 75 percent for several days.

Many have blamed the delays on military exercises — a claim initially confirmed by state media and authorities. But the government has since backtracked and is now attributing the flight backlog to an assortment of vague causes.

In a statement Tuesday, China’s Defense Ministry acknowledged that it is kicking off week-long military drills off the country’s southeastern coast but insisted that had nothing to do with the airport slowdowns. Rather, it blamed bad weather.

A whiteboard at Shanghai Hongqiao International Airport displays information about cancelled flights Tuesday. (Aly Song/Reuters)

The latest turmoil is compounding a recurring problem for China’s airports and airlines, which are not known for their punctuality. In a June 2013 report by the U.S. group FlightStats, Beijing Capital International Airport and Shanghai Pudong International Airport came in last for on-time performance among 35 major international airports. More than 80 percent of flights at Beijing’s airport failed to leave on time, according to the report. And Shanghai’s flight delays followed closely behind, with a tardiness rate of 71 percent.

All those flight delays, coupled with poor services from airlines, have produced a unique breed of seething passengers. Confrontations between airline staff and stranded passengers demanding explanations and compensation aren’t uncommon. Over the weekend, as many flights were delayed in the city of Shenzhen, passengers tired of vague answers and a lack of information became violent, resulting in several injuries, according to local TV reports.

Often contributing to the anger are rumors that quickly spread in the absence of official updates: that some party official held up the flight because he or she was running late, for example, or that authorities were trying to prevent a corrupt official from fleeing with cash.

The broader explanation for China’s chronic airport delays is the government’s severe restriction on airspace. The military controls 80 percent of the country’s airspace, leaving civilian aircraft little room to maneuver, according to a state media interview with China’s civil aviation minister in June. Meanwhile, airlines have been steadily adding flights to meet booming demand among China’s growing middle class.

But to blame the government publicly for such problems has proven to be unwise and even outright dangerous.

When this month’s delays first began, rumors abounded that the government had shut down the airspace to capture a senior military official on the run. Two Web users were later detained and 37 punished after being accused of spreading rumors, and more than 30 other Internet users received warnings about “fabricating rumors,” according to state-run Beijing Youth Daily.

China is performing its aerial military drills against the backdrop of growing tension with neighboring countries. As the nation celebrates the founding of the People’s Liberation Army on Aug. 1, the navy is conducting drills in all four seas in the east, including near Vietnam and Japan. Since June, the army also has been carrying out massive drills, which will last three months.

Passengers play poker Tuesday while waiting at Shanghai Hongqiao International Airport. Authorities announced that air traffic capacity at Shanghai airports would be cut down by 75 percent for several days. (Aly Song/Reuters)

The official microblogging account of PLA Daily on Tuesday posted a message asking people not to play up the link between the air traffic delays and Chinese military exercises. “We believe most web users are rational and will not hold the army fully responsible for the delays,” it said.

But Web users were not buying it. “Why don’t you just admit that military drills are causing flight delays? What’s wrong with owning up to it?” one user commented.

Xu Yangjingjing and Xu Jing contributed to this report.