Tech stops: where long flights stop, and why

A technical stop is a landing for fuel, and sometimes crew or a check, with no passengers joining or leaving. It is what an aircraft does when a leg is longer than it can fly, and for most of aviation's history it was routine: early airliners crossed oceans in hops.

The famous ones

Gander in Newfoundland and Shannon in the west of Ireland grew up as the two ends of the propeller-era North Atlantic, the last fuel before the ocean and the first after it. Shannon kept a role long after: British Airways' all-business-class A318 from London City to New York stopped there westbound, because the short runway at London City limited the fuel it could take off with.

Anchorage was the stop between Europe and Japan for the decades when Soviet airspace was closed to Western airlines, which made the polar route via Alaska the only practical one. Its airport is still among the busiest cargo stops in the world, a natural halfway point on the great circle between Asia and North America.

What makes a good stop

Three things. The airport has to be able to take the aircraft. It has to be close to the route, or the stop costs more distance than it is worth. And it has to split the leg into two parts that each clear the aircraft's range with reserves, which rules out a field just after departure even when it lies right on the track: nobody stops for fuel twenty minutes after take-off.

Overfly applies exactly those tests. A candidate is a large or medium airport with a runway of at least 6,000 ft, within 400 nm of the great circle, where neither leg is shorter than 15% of the whole and both clear usable range. The ones that pass are ranked by the extra distance they add.

On Sydney to Los Angeles, 6,512 nm, the Falcon 8X and 7X cannot make it non-stop. Overfly's best single stop for both is Nadi in Fiji: 1,711 nm to get there and 4,802 nm on to Los Angeles, with Nadi so close to the great circle that the detour rounds to nothing. Each route page lists the best stop for every type that needs one, or says when one stop is not enough.

Why they became rare, and when they still pay

Long-range twins all but ended the scheduled tech stop. Singapore to New York JFK is 8,283 nm on the great circle and is flown non-stop; Qantas has announced non-stop Sydney to London, 9,190 nm. A stop costs a landing, fees, the fuel to climb back to cruise, and an hour or more on the ground, and passengers will pay to skip it.

It can still be the better answer. Fuel is heavy, and carrying fuel to burn later costs fuel to carry. On a leg near the edge of an aircraft's range, the fuel load can force payload off; split the leg and each half needs far less fuel, so the aircraft can carry more passengers or freight than it could non-stop. That is the trade the London City service made at Shannon, and the one freighters still make at Anchorage.

What the suggestion leaves out

Ranking by extra distance can favour a stop near one end, which splits the leg unevenly. Auckland to New York LaGuardia, 7,675 nm, is just beyond a Gulfstream G650ER's 7,300 nm usable range, and Overfly's least-detour stop is Waco, Texas: 6,422 nm and then 1,253 nm, right on the great circle. It works for range, but an operator may prefer a midpoint to balance fuel, or a field with better handling, customs or fuel price. The mapper gives three candidates and lets you take one; the route is rewritten through it and checked again.

With seasonal winds on, each half is judged on air distance, so a stop that clears on paper but not into the month's headwind is not offered. See usable range for why.