Singapore Airlines flight SQ22, taking off from the airline's hub early tomorrow for New York, will be the world's longest commercial flight - and there's no risk of ending up in the cheap seats.

The Airbus A350-900ULR (for "ultra-long-range") is fitted with 67 business class seats and 94 premium economy - but no economy, reflecting the airline's aim of attracting passengers paying premium fares.

A plane this size can typically carry about 300 passengers in three classes, but Singapore has to allow for the extra fuel the ultra-long-range version carries, enabling it to stay in the air for more than 20 hours.

This is the route the first flight will take tomorrow morning. Photo / Supplied
This is the route the first flight will take tomorrow morning. Photo / Supplied

The airline says the flight track will cover up to 16,700km and take up to 18 hours and 45 minutes, depending on weather. That distance eclipses the 14,500km Auckland-Doha service that Qatar Airways has been flying for the past 18 months.

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Tomorrow morning's flight will be a slightly shorter distance and will take the North Pacific route. Captain S L Leong is commanding the flight and told journalists this afternoon the flight should benefit for strong jet stream tail winds of up to 200kph over North Asia and could take just 17 hours.

''We'll take the most efficient route and after we take off we'll fly in a north easterly track over the South China Sea, Japan, North Pacific, Alaska, north Canada and then on to New York,'' he told the Herald.

''It looks as if it's going to be 17 hours according to our latest flight plan. The time will depend on wind conditions.'

He said the A350 was a ''beautiful plane to fly.''

It will be the first commercial flight by any airline of the ULR on the route which lands at Newark, New Jersey - about 25km from Manhattan.

What's special about the plane?

The A350-900ULR is similar to planes such as the one that Cathay Pacific flies into Auckland every day; it's a lightweight, largely carbon fibre plane that is fuel-efficient, but it has important modifications.

In order to increase the fuel-carrying capacity, Airbus repositioned the sensors within the existing tanks and made some changes to the air venting and piping in the wing. It allows an additional 24,000 litres of fuel at take-off, for a total of 165,000 litres, without the need for additional fuel tanks.

The world's longest flights

There are also aerodynamic tweaks, including larger upswept winglets to reduce drag. The plane is powered by Rolls-Royce XWB engines, which as of the middle of this year had 99.89 per cent reliability since being introduced in 2015.

Airlines never pay list price, but if you walked in off the street Airbus would charge about $490 million for this plane.

Why this route?

Linking the two global financial hubs has been done before, but it lost money. Singapore Airlines flew the route from 2004 to 2013, using four-engine Airbus A340-500 aircraft. At first they had 181passengers but later the airline switched to a 100-passenger business class-only layout.

It was popular with the lucky few who flew it (and the six-member flight crew who worked short shifts) but wasn't sustainable, especially when the global financial crisis hit.

An airline spokesman said that when Singapore operated the route, it was happy with the demand for the A340s.

''However, the economics were challenging, and we returned the aircraft to Airbus. The new-generation A350-900ULR is a twin-engined aircraft that is significantly more efficient, enabling the ultra-long-range flights to be operated in a commercially viable manner,'' he said.

Since announcing the re-launch of the service this year, the airline had been pleased with the continued growth in bookings.

Will this be a game changer?

It is only a slightly longer trip than a growing number of ultra-long-haul routes, but other airlines will be closely watching the performance of the aircraft.

Air New Zealand is in the market for long-haul planes to replace its 777-200s early next decade and has aspirations to fly as far as New York from Auckland.

Qantas has also challenged planemakers to come up with aircraft to get from Sydney to New York or London, flights of 20 hours.

But for the Australasian airlines the leisure market is important - a plane with 161 premium seats wouldn't work; they would need to carry more passengers.

What 's the Singapore Airlines cabin like?

All A350s are roomier, with steeper sidewalls and bigger windows than most others (although not as big as Boeing Dreamliners) and are pressurised to a lower altitude than usual, which helps fight fatigue.

The low density seating of the Singapore Airlines A350 does set it apart from others and there are more creature comforts.

Business Travel: The future of ultra long flights

The airline says that in business class it will be adding a mattress topper for greater comfort, as well as providing two pillows - one firm and one soft.

In premium economy there is more in the amenity kits and seats have been updated and now feature a modified calf rest and a larger table.

How else can passengers enjoy the trip?

As part of a focus on "wellness cuisine", rest and relaxation, and general wellbeing, the airline has teamed up with retreat operator Canyon Ranch, ''to re-invent ultra-long-haul travel '', and enlisted the help of a former US Surgeon General.

Science-based strategies for improved sleep, exercise and stretching, as well as new nutrition-focused menus will be used.

Singapore Airlines captain of the first A350-ULR flight S L Leong. Photo / Grant Bradley
Singapore Airlines captain of the first A350-ULR flight S L Leong. Photo / Grant Bradley

Canyon Ranch chefs and nutritionists focused on nutrition and hydration (taking into consideration longer flight duration with less body movement), combined with bold flavours and textures.

Guided stretching exercises will be available to promote relaxation, led by Canyon Ranch exercise physiologists, accessible via personal seatback entertainment systems.

What about the lobster?

It needn't be a near 19-hour health retreat. Lobster thermidor is on the menu and can be ordered in advance. It comes sautéed in butter, flambéed in brandy, sprinkled with cheese and served with creamy mushroom sauce, garlic and spicy mustard, with buttered asparagus. Singapore Airlines crew at its training centre when asked what the most popular dish was were unanimous - Lobster Thermidor.

• Read more: Ultra-long-haul grows

Which way will the plane go?

There are three possible routes, depending on various considerations such as wind strength, and the flight could travel over the North Pacific, and traverse Russia and the Atlantic. Flight time could vary between 17h 30m and 18h 45m, depending on the conditions.

What about the crew?

There will be four pilots working in rotation. The Singapore Airlines spokesman said all qualified A350-trained pilots will be rostered for ULR flights as the plane does not require any additional pilot training, and the same goes for the 13 cabin crew usually on board. There will be two extra flight attendants on the first flight.

''However, we have required crew operating on the non-stop flights to undergo a fatigue management course. In comparison with a long-haul flight, cabin crew operating the ultra-long-haul flights will be given an extra hour of rest, which will be taken in the crew bunks.'

Look out for updates from the world's longest flight tomorrow