A day after an attempted plane hijacking came to light, the acting head of the mainland's civil aviation authority called yesterday for passengers to co-operate with security measures at airports. Li Jiaxiang , acting head of the General Administration of Civil Aviation of China (CAAC), said the administration had put in place effective and comprehensive safety measures. Without directly responding to questions about an apparent security loophole that saw a Uygur woman succeed in taking cans of petrol through an airport security check and onto an aeroplane, Mr Li said experts had been invited to carry out further investigations. 'I appeal to the public at large to show understanding and to co-operate with the security measures the CAAC has put in place,' he said. On Sunday, Xinjiang region chairman Nuer Baikeli said authorities had thwarted an attempt to down a China Southern flight from Urumqi to Beijing on Friday. The plane had to make an emergency landing in Lanzhou , the capital of Gansu province . According to sources, one of the four Uygur suspects had taken cans of petrol onto the plane. The latest case has raised concerns over China's susceptibility to terrorist attacks, and the possibility of Xinjiang separatists stepping up attacks ahead of the Olympics. However, Yu Linxiang , former political commissar of the Lanzhou military region, said the country had an 'inescapable dragnet' and any person who wanted to carry out terrorist activity would be crushed. With the Olympics only a few months away, Beijing Vice-Mayor Liu Jingmin said organisers had a comprehensive security plan in place. While saying security measures at airports were adequate, Mr Liu said they would be improved to make them safe and convenient for tourists. 'We have drawn up effective and comprehensive plans regarding anti-terrorism measures. We are also in talks with the law-enforcement authorities in other countries to strengthen co-operation. We believe we will give the world a safe Olympics,' Mr Liu said. When asked if China would seek other countries' help to fight terrorism during the Olympics, Vice-Minister of Foreign Affairs Wu Dawei said that ensuring a smooth and successful Olympics was a key foreign policy objective this year. 'There will be over 100 state leaders coming to attend the Olympics. We will do everything we can [to ensure their safety],' Mr Wu said.