Carrying just 81 passengers, the Airbus 340-500 aircraft fitted with 100 seats flew non-stop for 18 hours and is scheduled to arrive in the United States just before 6pm local time.

The return flight SQ21 will leave New York at 11pm the same day, the airline said in a statement.

The passengers are also able to use their iPods and iPhones onboard via the in-flight entertainment system, KrisWorld - for the first time on SIA flight. This will be extended to the SIA's Los Angeles-Singapore non-stop flights from August.

When it announced its decision in March to strip economy seats from its non-stop routes to the US, SIA said it was in response to strong demand for business class seats on the flights.

The airline launched its non-stop flights from Singapore to the US - New York and Los Angeles - in 2004.

With the conversion to all-business class flights, SIA's five A340-500 aircraft with 181 seats in two classes, are being reconfigured with 100 business class seats.

Each 76cm-wide seat converts into a fully flat bed. They are arranged in a 1-2-1 configuration so every passenger has direct access to the aisle.

SIA's executive vice-president for marketing and the regions, Mr Huang Cheng Eng, said that the direct flights to the US have always been well-received, adding that the reconfigured aircraft will allow SIA to increase its business class capacity.

For now, the all-business class aircraft will fly three times a week to New York, and daily by end-June.

By late September, SIA will also operate new flights to Los Angeles.

Economy passengers will then have to fly via Frankfurt, Germany to New York. Flights to Los Angeles stop in Narita, Tokyo.