Delta Air Lines is to start daily flights between Heathrow and Philadelphia next spring.
The city will become the carrier’s eighth destination in the US served from the London hub when the service starts on April 8.
The new connection means the partnership between Delta and Virgin Atlantic will offer 39 daily flights to 16 destinations across North America from the UK next summer.
The Philadelphia service will operate from Heathrow Terminal 4 using a 164-seat Boeing 757-200.
More than four million people have flown on the Delta-Virgin Atlantic partnership so far.
The US carrier’s Europe, Middle East and Africa senior vice president, Perry Cantarutti, said: “We are almost one year into our joint venture with Virgin Atlantic and our commitment to improving connectivity between the UK and United States remains as strong as ever.
“By starting flights to Philadelphia, customers not only have more choice on this route, but it also offers greater access to the northeastern corner of the United States.”