Delta Air Lines appears poised to become the fourth U.S. carrier to start nonstop flights to mainland China, the United States' largest Asian trading partner.

Delta hopes to start flying in spring 2008, possibly sooner, from Atlanta, its hometown, to Shanghai. It would give the Southeastern U.S. its first non-stop air link to Chinese markets.

Delta, the United States' No. 3 carrier, will submit its application for China flights to the Department of Transportation on the July 16 deadline. Later this year, the DOT will name a new U.S. airline to serve mainland China.

Jon Ash, a Washington, D.C., aviation consultant familiar with the route competition, says Delta is widely expected to win approval in the next round of DOT awards.

Delta is the only major U.S. airline not already serving China that is planning to apply for new service this year, so its selection seems very likely. "Delta is due," Ash says.

Tempe, Ariz.-based US Airways is another major carrier without nonstop flights to mainland China. But spokeswoman Andrea Rader says her airline won't compete with Delta for this year's China rights. Instead, the carrier will focus on competition for rights to be granted by DOT for flights to begin in 2009. "China is a big endeavor for us, so we want to do it right," she said.

Air service between the U.S. and China is restricted by agreement between the countries, but the restrictions are loosening and will continue to do so in the next 2 1/2 years. By the end of this decade, all six U.S. network carriers are expected to have daily flights to mainland China. United Airlines launched the most recent new route to China in March, from Washington Dulles International Airport to Beijing. American, United and Continental operate nonstop China flights from Chicago, Newark, N.J., and San Francisco. Northwest flies from several U.S. points to China through Tokyo.

Delta, the world's top carrier across the Atlantic, offers little Asia service today. Delta this year began flights to Tokyo and Seoul. Delta proposes to operate the daily, 15-hour Atlanta-Shanghai flights with Boeing 777s carrying 268 passengers, including 50 in a business-class cabin with lie-flat seats. It has sales offices in the U.S. and China ready to book the flights, and has a Mandarin Chinese Web site.

"We are ready to start the service whenever it's required," says vice president Doug Blissit.

Delta, which emerged from Chapter 11 bankruptcy restructuring in May, has been gearing up for China for years. U.S. airlines see annual revenue potential of $100 million or more in China routes, with China's aviation system expanding faster than that of any other country.

Under the U.S.-China agreement, the Department of Transportation will award China rights by next year for a U.S. carrier to fly to Guangzhou, China's third-biggest city. In 2009, there will be openings for one new U.S. carrier to China, and for another U.S. carrier already flying there to expand service.