A marathon 19 hours -- The world's longest commercial flight from Singapore to New York is resuming again, for the first time in five years.

Singapore Airlines has ordered seven new ultra-long range twin-engine Airbus A350s for the route -- There's no economy class on the plane -- just 161 business and premium economy seats, and the airline is also restarting non-stop flights to Los Angeles next month.

It abandoned two marathon Singapore routes to the U.S. in 2003 because of high fuel prices.

Still 19 hours might not be the longest for long, Qantas Airways is considering the introduction of a 20-hour Sydney to London flight from 2022.