Delta has relocated some of its key services to Heathrow Terminal 3 where it joins its transatlantic partner Virgin.
The move, designed to "enhance convenience and a seamless customer experience", comes as both airlines start flying their new summer schedules from today.
Both Delta and Virgin Atlantic now operate their LHR to New York JFK services from Terminal 3, making it easier for passengers to manage any last minute flight changes.
Delta president Ed Bastian said: "From the outset of our partnership with Virgin Atlantic we have been committed to putting the customer first and creating more competition on transatlantic routes.
"The co-location of our key business flights with Virgin Atlantic at Heathrow is another step forward in delivering against these commitments. Together we are offering new routes and more flights this summer and making a real difference for customers."
The two airlines' summer schedule includes a total of 32 peak daily non-stop flights between North America and the UK. Of these, 25 flights will operate between LHR and US destinations such as Los Angeles, San Francisco, Atlanta and Washington.
Craig Kreeger, Virgin Atlantic's CEO, said: "Today marks another important step in our joint venture with Delta. We're really pleased to welcome Delta customers into our home at Terminal 3 to enjoy a shared experience of our award-winning Clubhouses and industry-envied customer service.
"Virgin Atlantic prides itself on seamless journeys for our customers and we can now extend that to Delta's New York, Boston and Seattle customers through an enhanced flying schedule and smoother connections.
"Couple these factors with our onboard experiences and we're confident our joint venture is the best transatlantic offering in the marketplace."