Shanghai opened a new terminal at its domestic airport on Tuesday as China's second-largest city geared up to welcome tens of millions of visitors to the Expo 2010.

The government has spent 2.2 billion dollars on the makeover of Hongqiao Airport, 35 minutes west of the city centre, and made it part of an ultramodern travel hub linking metro and high-speed rail.

"An airport with the size of a world-class hub has taken shape, which will provide a high-quality aviation service for the World Expo," said an airport authority statement.

The first flight from Hongqiao's new terminal - four times bigger than the cramped old facility - took off early Tuesday for Beijing.

Pudong Airport is Shanghai's main airport for international flights while Hongqiao is used mainly by domestic airlines. Officials expect the vast majority of the Expo's 70-100 million visitors to come from within China.

Hongqiao, which means rainbow bridge in Chinese, is expected to handle 40 million passengers a year by 2015, three-quarters of whom will use the new, four-level terminal.

The old terminal was designed for 9.6 million passengers a year but last year handled more than 25 million.

A direct metro line into the building also opened Tuesday, linking the airport to the city by subway for the first time.

The new terminal and a second runway are among a chain of projects that will see up to 400 billion yuan (58 billion dollars) in direct and indirect investment in the Expo, according to state media - more than the 290 billion yuan reportedly spent on the 2008 Beijing Olympics.

Shanghai is spending nearly 300 billion yuan to expand its subway system alone, adding hundreds of kilometres (miles) of new tracks for new and extended lines ahead of Expo, which runs for six months.

High-speed trains are due to start arriving at the airport from the eastern city of Nanjing on July 1, with trains from Beijing scheduled for next year.