For the next three weeks at least , flying to and within China is going to be a stressful affair , for even the hardiest of travelers . Hundreds of flights were canceled or delayed Monday and China 's civil aviation regulator warned that more flights in 12 airports will be affected over the coming three weeks . The worst affected airports so far have been Shanghai 's two airports -- Pudong and Hongqiao -- two of the country 's busiest airline hubs . Another 120 flights were delayed for more than two hours . Domestic travelers have been switching to high-speed trains ( Chinese only ) after hearing of the widespread delays , leading to severe overcrowding on main rail routes some have likened to the Chinese New Year migration . Officials and airlines have shed little light on the reasons for the disruptions but local media have suggested the cause is due to military exercises . Speculation is rife on social media . `` Perhaps I 'm ill-informed but I 've never heard of any other countries ' military exercises affecting civil airlines on such a large scale , '' posted user @ luoyu on Weibo , China 's version of Twitter . `` I 've also never seen such vast adjustments affecting a quarter of civil airlines ' flights in China 's history . Whatever is causing the wide-scale delays , it 's making history . '' What 's going on ? Local officials cited `` air traffic restrictions '' while Shanghai-based China Eastern Airlines said `` the airspace was occupied , '' according to the Shanghai Daily newspaper . `` Among situations for air traffic restrictions being imposed are when military maneuvers are taking place , '' the newspaper added . CCTV , the state television channel , shared on its Weibo account -- China 's equivalent of Twitter -- a widely circulated memo , originally published on a Chinese flight crew blog , that said the civil aviation authority has requested airlines to reduce flights by 25 % in eastern China . Hundreds of flights to and from eastern China were canceled or delayed Monday , with 200 flights canceled at Pudong and Hongqiao . Flights departing from other eastern Chinese cities ' airports , including Nanjing and Hangzhou , were also affected . MORE : And the world 's best airline 2014 is ... Where to expect delays . `` The following 12 airports will experience massive delays for 26 days ! Fliers , bring snacks and water ! '' the CCTV post said . `` From July 20 to August 15 , operations of these airports -- including Shanghai Hongqiao , Shanghai Pudong , Nanjing , Hangzhou , Hefei , Jinan , Wuxi , Ningbo , Qingdao , Lianyungang , Zhengzhou and Wuhan -- will be affected by high-frequency exercises conducted by another party . All airlines are requested to reduce flights by 25 % and fliers are expected to face delays . '' Officials at the Civil Aviation Administration of China declined to comment when approached by CNN . Past delays . This is the second large-scale air traffic disruption in China in the last two weeks . More than 100 flights were canceled or delayed on July 14 in Shanghai . In December 2006 , Shanghai Pudong International Airport closed and hundreds of flights were canceled or delayed due to military exercises . Two Internet users have been held by police for allegedly fabricating and circulating `` anti-corruption-related '' claims , according to Hong Kong newspaper South China Morning Post . The Internet users claimed the disruption was due to the arrest of a high-ranking government official trying to flee the country . Another 37 people were reprimanded in the crackdown against Internet `` rumor mongers , '' according to SCMP . China 's air traffic woes continue . Lengthy flight delays are common in China . The country 's largest airports , serving the mega-cities of Shanghai and Beijing , suffer some of the worst flight delays in the world . In June 2013 , Beijing 's Capital International Airport hit the bottom of a list of the world 's most delayed airports , according to U.S.-based air travel information service FlightStats . Just 18.3 % of flights from the airport left on time during that month and around 42 % of flights suffered delays of 45 minutes or longer . Second worst on the list was Shanghai 's Hongqiao , where just 24 % of flights departed on time . Overly cautious air traffic control and airspace restrictions for civilian aircraft are two of the reasons for these delays , but flights are also affected by thick smog and once , an unidentified flying object ( UFO ) . MORE : Delayed ! Why flying in China is hard .
Military exercises thought to be behind China flight cancellations and delays for next three weeks . Domestic travelers switching to train travel , leading to overcrowded trains . 12 airports in China to be affected , including both Shanghai airports .