The only helicopter landing on the summit of Everest

Ask whether a helicopter can land on Mount Everest and you get two confident, opposite answers. Both are wrong in the way that matters. It has been done — once — and it is not something you can buy a seat on.

Didier Delsalle, a test pilot for what was then Eurocopter, flew a production AS350 B3 from Lukla to the summit of Everest and set it down on the snow at 8,848 m. He held it there for close to four minutes, which mattered: the Fédération Aéronautique Internationale requires the aircraft to settle, not touch, for a landing to be certified.

He did it again the next day, because a record has to be repeatable to be ratified. Then he flew home and the industry moved on.

The aircraft was a standard B3 with everything removable removed: no passenger seats, no cargo, the minimum fuel that would get it up and back down. One pilot, no crew.

That is not a technicality. At 8,848 m there is about a third as much air per cubic metre as at sea level, so the rotor makes about a third of the lift, and the engine — burning the same thin air — has correspondingly less power to spin it with. The margin Delsalle flew in was measured in kilograms.

The flight proved a point about the B3's engine at altitude, and the point stayed proved. There was no commercial demand to repeat it, because there is no version of a summit landing that carries a passenger.

There is also the small matter of the weather. From October to May the jet stream sits directly on the summit ridge at over 160 km/h. Delsalle had a window; most days do not have one.

The useful legacy is not the summit. It is what the same aircraft type does at 5,000 to 6,500 m, day in and day out, in the hands of Nepali crews: base camp landings, Camp 2 evacuations, and longline extractions from ground no aircraft can touch.

That is the flying that saves lives in the Khumbu every season, and it is the reason the B3 and its successor the H125 are the aircraft you will find yourself sitting in on an Everest morning.