Why did airplane's window break?

An investigative group set up by the Civil Aviation Administration of China has arrived in Chengdu, Sichuan province, to look into why the front windshield of an Airbus A319 blew out on Monday morning, Tang Weibin, head of the administration's safety office, said on Tuesday.

Aircraft windshields are made of several layers of tough material and are extremely hard to break. The one that blew out was original and had no record of problems or repairs, a preliminary investigation found.

Sichuan Airlines Flight 3U8633 took off as scheduled from Chongqing Jiangbei International Airport in Chongqing municipality at 6:26 am and was due in Lhasa, Tibet autonomous region, at 9:05 am.

The cockpit windshield shattered about 7 am, about 100 kilometers into the journey, nearly sucking a co-pilot from the plane. The aircraft, which had been traveling at 800 to 900 kilometers per hour, abruptly lost altitude for five or six seconds.

According to the captain, Liu Chuanjian, "everything in the cockpit was floating weightlessly in the air, and most of the equipment malfunctioned".

"I couldn't hear the radio," Liu said. "The aircraft was shaking so hard I couldn't read the gauges."

He was able to make an emergency landing at Chengdu Shuangliu International Airport about 45 minutes after the incident, saving all 119 passengers and nine crew members aboard.

Aviation authorities responsible for China's southwestern region sent urgent messages on Monday to aviation companies and maintenance units, telling them what happened and asking them to be vigilant to prevent similar incidents and requiring aircraft maintenance personnel to screen related parts to get rid of hidden perils.

"My colleagues and I were shocked to learn of the incident and we do not know why it took place. After every flight, we check the windshield to see if it has a crack or scratch or if one layer of glass is separated from another," said Zhang Yi, a Chengdu resident who has maintained aircraft at Chengdu Shuangliu International Airport since 1990.

"If there is any problem, we would replace the windshield," he said.

Wang Yanan, chief editor of Beijing-based Aerospace Knowledge magazine, thought a defect might have appeared in the windshield when it was being made or installed.

Installation of a windshield requires metal fasteners. If something abnormal happened where the windshield and a metal part met, it could damage the entire windshield, he said.