The jetliner departed Paine Field in Everett on Wednesday, arriving at London's Heathrow Airport today at 12:10 p.m. local time.
The London-based airline has ordered 24 Dreamliners from Boeing.
British Airways has announced that the airline will operate its first 787 from Heathrow to Toronto from Sept. 1 and Heathrow to Newark from Oct. 1.
Todd Nelp, vice president of European sales for Boeing, called the delivery of the plane "an exciting milestone for Boeing and British Airways."
British Airways operates more than 140 Boeing airplanes within its fleet including 52 777s, as well as the world's largest fleet of 747s with 52.
In addition to the 24 Dreamliners already on order, British Airways also recently announced that it will convert 18 options to firm orders for the 787. Twelve of these will be 787-10s, meaning British Airways will operate the entire 787 family - the 787-8, 787-9 and 787-10.
British Airways employs approximately 40,000 people, based mainly in the UK, although it has staff based in more 75 countries around the world. The airline's route network currently serves in excess of 177 destinations and it operates in excess of 300,000 flights per year.