Delta Air Lines is to increase the number of departures from the Chinese mainland and Hong Kong to 49 a week when it launches daily direct flights from Shanghai to Seattle in June.

The Atlanta-based airline now operates 39 departures from the Chinese mainland and Hong Kong on a weekly basis.

That will be the fourth direct route between China and the US after Beijing to Seattle and Detroit as well as from Shanghai to Detroit, the company said.

"And we are going to discuss more flight plans with our partners in China," said Ryoko Matsumoto, the airline’s corporate communications manager. Delta has partnered with China Southern Airlines and China Eastern Airlines on the Chinese mainland.

The major US airline unveiled a renewed terminal in New York on May 24.

The terminal has seven direct flights a week to Narita Airport in Tokyo, the company’s Asia-Pacific hub from where travelers can reach most major destinations in Asia, said Vinay Dube, senior vice-president Asia Pacific of Delta Air Lines.

"And in the next few years there is very strong possibility that we launch direct flights from New York to China," he added.

The opening of the renewed terminal at JFK International Airport came more than a month after the US Secretary of State John Kerry called for more Chinese investment in the US during his first trip to China in April after he took office in February.

The terminal will be instrumental in attracting Chinese investors, said local officials.

"Infrastructure improvements like this terminal by Delta are very important for increasing the number of business travelers as we see in New York City and New York State," said Kenneth Adams, commissioner of the New York State Department of Economic Development.

"There are also growing opportunities to develop relationships with provincial governments, with Chinese trade authorities and investment groups who are looking at different sectors of American economy," Adams added.

As the world economy recovers and Sino-US relations improve, the North American country has seen a steady rise in the number of Chinese visits.

The US embassy and consulates in China handled more than 1.36 million non-immigrant visa applications in 2012, up 34 percent from 2011.