The new American flight to Miami airport will operate on a daily basis and will mean five flights a day are on offer between the two airlines from October 27 to March 28.
Miami is one of the airline’s hubs and serves as the gateway to its Caribbean, Mexican and Latin American services, with 350 flights a day operating to 130 destinations in 43 countries.
Meanwhile, BA is offering three additional weekly flights to Philadelphia on Wednesdays, Fridays and Sundays during the same period.
Once they have touched down in the US, travellers can then take advantage of any of the 400 daily flights to connect elsewhere.
Rhett Workman, American Airlines managing director of London Heathrow, said: “This will be American’s biggest year yet at Heathrow with an additional flight to Miami and new year-round service to Phoenix.
“We’re not only giving customers in the UK increased access to the warm winter-sun destinations they want, but also working with our partner British Airways to better meet the demand for premium seats in important markets and connecting hubs like Philadelphia.”