The low-cost airline, Norwegian, has stepped up its battle against the existing transatlantic airlines by announcing two new routes from Gatwick to the US.

From 16 September 2017, it will fly to Denver — initially twice a week, but with an added service in winter, when the Colorado airport is popular with skiers.

The following day, the first Gatwick-Seattle service will begin — flying four times a week to the biggest city in Washington State, which is home to Amazon and Microsoft.

British Airways flies to both cities from Heathrow. Virgin Atlantic has just taken over the Heathrow-Seattle route from its partner, Delta.

Norwegian says its current US schedule is operating at over 90 per cent full. Earlier this week, Bjorn Kjos, CEO of Norwegian, hinted he was looking at longer-range links, saying: "The Dreamliner has a low operating cost with enough range. The aircraft is built for 18-hours utilisation."

The airline’s chief commercial officer, Thomas Ramdahl, said: “We are excited to add Seattle to our growing list of US destinations while breaking the monopoly on UK flights to Denver.”

“As we expand our high-quality services to the USA, we will continue offering passengers greater choice, convenient schedules and affordable fares.”

Gatwick is seeking to expand its long-haul network, particular on business routes.

Guy Stephenson, the airport’s chief commercial officer, said: “Both cities are prominent business centres known for their hi-tech and advanced manufacturing industries. Both are also gateways for trade across the US so this new connectivity comes at an important time for UK businesses, including those that export cargo.”