He said the plane had to return to Beijing in the interests of safety and landed without incident. Passengers were transferred to another plane, which took off at 1.35pm and arrived safely in Shanghai. 'The precise cause of the fault is being investigated,' the spokesman said.

One passenger said a noise like a loud boom was heard while the plane was on the taxiway before take-off. The pilot announced the plane would turn around and land in Beijing. It had to be towed after landing.

The incident happened only three days after a Hong Kong-bound Shanghai Airlines Boeing 767 had to return to Shanghai 35 minutes after taking off because of equipment failure. An airline spokesman said the crew had noticed some mist around air outlets and had decided to return because of safety concerns. A passenger said there had been a short circuit, explosion and smoke in the aircraft.

The mainland's aviation safety has been put under scrutiny in recent weeks after a Henan airlines plane E-190 crashed in Yichun , Heilongjiang , with 96 people on board on August 24. Forty-two people were killed and an official probe is continuing.

The next day another E-190, operated by Tianjin Airlines, skidded off the runway during a landing in Nanning , Guangxi , with no reported injuries. Heavy rain and poor visibility were blamed.

Unsafe skies

Air safety has been under scrutiny since the crash in Heilongjiang

There have been this many incidents involving air safety in the past two weeks: 4