The National Stadium under construction.[BOCOG]

Construction of major Olympic projects including the National Stadium and National Aquatics Center, as well as the expansion of Beijing Capital International Airport have made smooth progress with timeline and quality guaranteed, officials said on Wednesday.

Steel structures are being installed at the National Stadium, the main stadium of the 2008 Olympic Games. Whilst work on the columns of vertical trusses is completed, installation of main roof trusses is still under way.

Preparation for the closure of main steel structures has been scheduled for the end of July, with an aim to finish all the work on steel structures by the end of the year, said Li Zhengquan, deputy manager of the project, also known as the "Bird's Nest."

Great changes have taken place with the main structure of the National Aquatics Center, or the "Water Cube." The installation of main steel structure is completed and the outline of the steel-made "water molecules" can be recognized. Workers are now busy installing the membrane structure, planning to finish the work by the end of the year.

Construction of Terminal No. 3 of the Capital Airport is in full swing. As important as any Olympic competition venue now under construction, the airport will undertake the arrival and departure of the Games participants in 2008, after its expansion is finished by the end of 2007.

The inauguration of Terminal 3 and the third runway will raise the airport's annual passenger throughput to 60 million from the current 35 million and its annual cargo throughput to 1.8 million tons from the current 780,000 tons.