Transport minister Karen Buck and Lord Coe joined London mayor Ken Livingstone to mark the occasion. "This extension is a vital transport link that has been delivered on time and on budget," said Livingstone. "We are now starting to see the benefits of Transport for London's £10 billion five-year investment."
The extension runs from Canning Town to King George V station at North Woolwich via London City Airport. It will play a key part in the city's plans for the 2012 Olympic Games.
The line now has four stations that connect local and airport passengers directly to the London Underground at Canning Town. The mayor added that the extension will open up access to jobs and housing in the area.