A second Heathrow-Philadelphia service is to be introduced by American Airlines next year.
The announcement came a day after Delta Air Lines unveiled plans to serve the US city from Heathrow from April 8.
The second American Airlines frequency on the route is to start on March 29 as a daily daytime Boeing 757 service from Philadelphia to London.
The route will continue to be operated as part of the airline’s joint business agreement with British Airways. Together, the two airlines will offer four daily flights year-round between the two cities.
American runs more than 475 daily flights to 124 destinations from its hub at the US east coast city.