The traveler who sets off from New York or London intent on flying around the world can do so in three hops. In the late 1980s, upgraded engines allowed Jumbo jets to reach Tokyo non-stop. From the Japanese capital, trans-Pacific flights opened up to Vancouver, San Francisco and Los Angeles. From any of these, you could make a final leap back to London or New York.
The catch, of course, is that it was a firmly northern hemisphere itinerary. And if you want to make a three-leg trip around the world, I cannot see any possible itinerary that crosses the equator. London-Singapore-Los Angeles-London gets close, but no cigar to celebrate reaching the southern hemisphere: Singapore is around 100 miles north of the equator.
Qantas begins the first UK-Australia scheduled non-stop Boeing 787 service on Mar. 25, 2018, with a special jetlag reducing menu, it will take just 17 hours from Perth non-stop. It would be tempting to speculate that a “proper” three-hop round-the-world trip becomes feasible. But the new flight goes from London Heathrow to Perth. Western Australia’s capital is short on the very long links that are necessary to reach the Americas. It is six hours flight from Melbourne, Sydney or Brisbane where you have good connections with the US west coast, Perth has few Pacific links.
Since Feb, 5 2017, the longest non-stop scheduled airline flight by great circle distance is Qatar Airways Flight 921/920 between Auckland, New Zealand and Doha, Qatar at 14,535 kilometres (7,848 nmi; 9,032 mi). The flights use a very long-range Boeing 777-200LR. QR 921 from Auckland to Doha is also the longest flight in duration, taking 18 hours and 20 minutes.
Twinjets have always flown across water, but initially they were not considered suitable for long trans-oceanic sectors: planes with three or four engines offered more resilience. But reliability has improved – along with the cost of aviation fuel. The twin-engined Boeing 777 or 787 and Airbus A350 or A330 are much more fuel-efficient than the four-engined 747 and A340.
Routings may avoid the shorter ground distance of a great circle route to use tailwinds to save time and fuel, shortening the equivalent still air distance. Air India‘s flights from Delhi to San Francisco can be routed over the Pacific Ocean rather than the North Pole over 15,000 km (8,099 nmi; 9,321 mi) rather than 12,395 km (6,693 nmi; 7,702 mi), similar to the 17 hours Qatar Airways QR 921’s distance, but taking 14.5 hours due to tailwinds.
Cathay Pacific flights from Hong Kong to New York City-JFK can fly 15,000 km (8,099 nmi; 9,321 mi) ground routes, rather than the 12,984 km (7,011 nmi; 8,068 mi) great circle route.
The South Polar Express won’t happen for a year or two. It may be that Qantas, having gained experience with the London link, decides to pursue the route, setting up an Antarctic race against a Norwegian opponent; not the first in that part of the world. Cape Town to Auckland is another trans-Antarctic possibility, with Air New Zealand a good candidate.