Mystery of glowing white ball in the sky.[Photo offered by Chinese microblogs]

A huge glowing UFO hovering high above Shanghai at around 9pm on Saturday was spotted by several civil aviation pilots who reported the sightings to the East China Air Traffic Control Bureau, Shanghai Daily reported.

A bureau official surnamed Jiang confirmed yesterday that they had received reports from several pilots. No flights were affected but he refused to disclose more details.

The unidentified flying object was 10,700 meters above Shanghai, and it grew bigger and bigger as time passed, a man who claimed he was a pilot on "Flight 6554" wrote on his microblog.

 

"The huge white ball suddenly appears in the sky when the airplane climbed out of thick clouds," he wrote. "It was several hundred times bigger than the moon, and human eyes can observe."

He said the object reached a diameter of at least 92 kilometers. About 20 minutes later, the shining ball became darker and gradually disappeared, he said.

"At first I thought it was just an illusion, but the copilot said he saw the same scene too," he said, "At least 10 pilots reported the object to the air control traffic bureau."

Meanwhile, people in Beijing reported seeing the object in the sky above the capital about the same time as the Shanghai sightings.

"The white round bubble appears in the sky and then expanded quickly, until it disappeared five minutes later," said Yu Jun, a former editor of a scientific magazine and amateur astronomer who took pictures of the object.

"I believe the glowing bubble is not just a natural astronomical phenomenon, but is a phenomenon occurring around Earth, perhaps in the upper atmosphere, caused by the launching of rockets or satellites," said Yu.

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Ma Jing, an engineer with the National Astronomical Observatories, said he took a set of pictures showing the object rise from the west like an "expanding round white cloud" but disappeared only several minutes later.

Zhan Xiang, an official with the Beijing Planetarium, said the "bubble might be caused by the substances emitted by military devices or satellites."

Some amateur astronomers said the object might have something to do with a satellite that had gone missing. China News Service reported that a Russian communications satellite, the Express-AM4, disappeared after takeoff early on Thursday morning.

(Shanghai Daily contributed to this story)