Delta Air Lines (NYSE: DAL) and Virgin Atlantic Airways will expand their partnership between the U.K. and U.S. next year with the introduction of Delta’s nonstop service from London to Philadelphia.

Starting on April 8, 2015 the daily service will be Delta’s eighth destination to the U.S. from Heathrow. By next summer, the partnership will offer 39 daily flights to 16 destinations across North America from the U.K..

“We are almost one year into our joint venture with Virgin Atlantic and our commitment to improving connectivity between the United Kingdom and United States remains as strong as ever,” said Perry Cantarutti, Delta’s senior vice president, Europe, Middle East and Africa. “By starting flights to Philadelphia, customers not only have more choice on this route, but it also offers greater access to the north eastern corner of the United States.”

Philadelphia has important historical significance as the place where the Constitution and Declaration of Independence were signed. It is also the fifth most populous city in the United States. Looking at international visitors, historically, the U.K. has been the primary source market to the area, which attracted 673,000 people in 2013, according to data compiled by the U.S. Department of Commerce, Office of Travel and Tourism Industries.                                          

The service to Philadelphia, which is already among the partnership’s top 15 onward destinations, is another step by Delta and Virgin Atlantic to strengthen their network between the U.K. and U.S.. Passenger choice was enhanced last month when Delta took over the operation of one of Virgin Atlantic’s two daily Heathrow-Los Angeles flights on the same day Virgin Atlantic started operating one of Delta’s three flights between Heathrow and its hometown airport in Atlanta. The airlines also started nonstop service from Heathrow to Seattle in March this year.

Delta’s London Heathrow-Philadelphia flights will operate as follows:

Delta’s Philadelphia service will be operated from Heathrow Terminal 4 using a Boeing 757-200 aircraft with 164 seats. Passengers travelling in the BusinessElite cabin will enjoy fully flat-bed seats and a range of dining options. Additionally, throughout the aircraft, all passengers will have access to on-demand in-flight entertainment.

To date, more than four million people have flown on the Delta-Virgin Atlantic partnership.

Customers can purchase tickets to Philadelphia and other U.S destinations through Delta Air Lines on 0871 221 1222 or www.delta.com