A breakdown of the longest plane journeys in the world reveals some of the more gruelling flights airline passengers are likely to take - with many covering close to 15,000km in a single trip.

The long haul list comes in the lead-up to the first flight of Singapore Airlines' Airbus 350XWB-ULR, which will carry passengers a record 15,332km from the runway in Singapore to the tarmac in New York.

Until then, though, three out of five of the world's longest flights all depart out of either Australia or New Zealand, reports the Daily Mail Australia.

Currently sitting in top spot is the leg from Auckland, New Zealand to Doha, in Qatar: a 14,535km route flown by Qatar airlines' colossal Boeing 777-200LR.

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The 18-hour international flight is the only one in the top five not undertaken by a Boeing 787-9.

The second and third longest journeys are only a fraction smaller, however: with flights from Perth, Australia to London and Auckland to Dubai - via Qantas and Emirates, respectively - each covering a total of 14,498km.

The transit between Los Angeles and Singapore is the world's fourth-longest at 14,114km, while the fifth-longest flight sees passengers travelling 13,834km from Houston to Sydney.

Both of the latter are provided by United Airlines.

Singapore Airlines' ultra-long haul leg from Changi Airport in Singapore to Newark Liberty Airport in New York is set to launch in October of 2018, steaming ahead to become the world's longest non-stop flight.

The plane will only provide premium seating, with no current plans to offer passengers an economy option.