Norwegian claims to have put the lowest London to Boston fare on sale at £179 one-way.
The Scandinavian budget carrier launches its Gatwick-Boston route on May 13, 2016 and has made fares available today (Tuesday).
The 787 Dreamliner service will depart on Mondays, Wednesdays, Fridays and Sundays.
The airline plans to add more than 60,000 seats on the route over the next six months as it moves to cut the cost of travel to New England.
Norwegian will also start direct services to Boston from both Copenhagen and Oslo.
Boston will become Norwegian’s fifth US destination following New York, Los Angeles, Orlando and Fort Lauderdale.
Chief executive, Bjørn Kjos, said: “Today we have launched the UK’s cheapest flight to Boston, helping to make this popular New England city affordable at long last.
“Norwegian offers the UK’s only low-cost, long-haul travel to the USA, and Boston will become our fifth new destination since introducing our pioneering flights last year.
“We expect Boston to be a popular addition offering an exciting new city break, and providing affordable access to the New England region for both business and leisure travellers.
“The cost of flying to America has been too high for too long, and the success of our transatlantic flights show there is huge demand for quality, affordable long haul travel.
“We are pleased to add Boston to our network from London Gatwick as we continue our exciting plans for UK growth.”