[article] The Chinese carrier Hainan Airlines has received federal approval to offer nonstop service from Boston to Beijing starting in June 2014, providing a boost to Logan International Airport’s global ambitions and the state’s strengthening economic ties to China. Hainan would initially offer four flights a week between the two cities, according to filings the company made to the US Department of Transportation last month. The federal agency approved the Boston service last week. The approval was first reported by the Boston Herald. Hainan would still have to sign an agreement with Logan’s operator, the Massachusetts Port Authority, before it could begin service from the airport. Massport officials declined to comment. Officials at Hainan Airlines could not be reached for comment Monday night.