Norwegian Air Shuttle's new transatlantic service has attracted controversy over claims it has circumvented international laws to its competitive advantage.

The first low-cost transatlantic flights since Freddie Laker's doomed Skytrain enterprise has left Gatwick airport for Los Angeles, a development that Gatwick describes a "game-changer" in the debate over where to build a new runway in London.

As well as the twice-weekly service to LA, Norwegian will operate two flights a week to Fort Lauderdale, where the majority of the cabin crew will be based, while a London-New York service has its first flight on Thursday.

The new operation from Norwegian Air Shuttle has attracted controversy, particularly in the United States, for taking advantage of differing international legislation to circumvent labour costs and buy aircraft on more favourable terms than competitors.

Consumers will also struggle to find a seat at the advertised cheapest fares, on the relatively few long-haul services that Norwegian runs. Only seven of its 95 planes are capable of transatlantic flights.

Norwegian will run a service pitched somewhere between the low-cost European model and traditional transatlantic carriers, with seat-back entertainment included but food and luggage incurring extra charges.

The airline's chief executive, Bjørn Kos, said: "At Norwegian, we believe that everyone should be able to afford to fly. In order to compete in the global airline industry you need to adapt to changes and keep a constant focus on cost.

"Norwegian has a low-cost model, meaning a lean administration, brand new and fuel-efficient aircraft and efficient operations. We fly direct routes with high passenger demand and choose centrally located airports such at Gatwick that share our mindset."

Kos says costs have been driven down by the fuel efficiency of the Boeing 787 Dreamliner plane.

The airline, which already operates similar services between Thailand, Scandinavia and the US, has come under fire in Norway and elsewhere for employing crew in Bangkok on Singaporean contracts. Unions have accused Norwegian of undermining labour conventions, with the ITF likening its pursuit of operating licences to the shipping practice of registering vessels under flags of convenience.

Norwegian said it established its long-haul company in Dublin for its air traffic rights as an EU nation and to maintain export guarantees to finance its fleet orders, and that the airline fully complies with European safety standards.

Pilots union Balpa said concerns remained, although a ruling in the US has prevented Norwegian from using pilots from Bangkok on the new Gatwick routes.

Balpa said: "The use of European pilots on this new route will reassure passengers who may otherwise have been concerned about an airline associated with a particular country by name which is in fact cherry-picking another country to oversee its safety standards and yet another to employ its pilots."

For Gatwick, however, the Norwegian long-haul launch is a milestone in its battle for expansion. Its chief executive, Stewart Wingate, said: "A low-cost carrier flying to the Big Apple for a small price shows how fast aviation is changing and highlights one of a series of future trends that will have a huge bearing on the UK's runways debate."

The airport unveiled a new report by independent aviation consultant Chris Tarry, which set out how the latest generation of aircraft could affect London airport expansion, with a fuel economy, size and range that lowers the need for connecting passengers and opens up the development of low-cost long-haul services.

Tarry's report says Gulf expansion would also lower the demand for connections in a London hub, but he believes that traffic will grow due to the strength of the capital as a destination in its own right.

Wingate added: "As this new report outlines, it is the airlines' fleet plans and order books of today that hold the key to the expansion needs of tomorrow. New generation aircraft and other key trends will lead to a reduction in 'hub' connecting traffic, an increase in point-to-point services and the continued growth of low-cost carriers, all of which are cornerstones of Gatwick's case for a second runway."

He added: "Heathrow's plans are yesterday's solution to tomorrow's problem and that only expansion of Gatwick can meet the challenges and demands of the future."