There is a category of object that can only travel by An-124. A satellite. A locomotive. A complete power station turbine. A Boeing 787 wing section. The rotor assembly for a wind farm. A concrete pump urgently required at a melting nuclear reactor.

Fifty-seven of these aircraft were built. The line closed. Nothing has replaced it, and this week the European Defence Agency effectively admitted that nothing is going to, at least not soon.

Built because the Americans had better ones

The An-124 exists because of a CIA assessment, or at least because of the reality the CIA described.

Soviet Military Transport Aviation in the early 1970s had about fifty An-22 turboprops as its heaviest lift, and they were being used tactically. Design work on a much larger aircraft began at the Antonov bureau in 1971 under Viktor Tolmachev, known internally as Izdeliye 400 and in the West as the An-40. Two assembly lines were built — Ulyanovsk in Russia, Kyiv in Ukraine — fed by components from over a hundred factories.

The first airframe went together in 1979 and flew on Christmas Eve 1982. The West got its first proper look at the 1985 Paris Air Show, where it was substantially larger than the C-5 Galaxy everyone had assumed was the ceiling.

What makes it irreplaceable

The obvious answer is size, and the hold is genuinely bigger than a C-5’s — 36 by 6.4 by 4.4 metres, about twenty per cent more volume. But size alone does not explain it.

It has doors at both ends, so a vehicle can drive in one end and out the other. The landing gear kneels, dropping the nose so the ramp angle is shallow enough to roll heavy plant aboard. There is an overhead crane in the hold rated at 30 tonnes and a winch system that can drag 120 tonnes in. The cargo floor is solid titanium — a material choice that is normally ruled out on cost, and which exists here because the alternative could not take the point loads.

And what makes it impossible

The same aircraft is an economic problem, and the numbers are brutal.

It carries a crew of eight. A pilot, a copilot, a navigator, a chief flight engineer, an electrical flight engineer, a radio operator and two loadmasters. A modern freighter of comparable size is flown by two people. Every sector therefore carries six salaries that no Western operator would price in.

The main cargo deck is only partially pressurised — 24.6 kPa — which is why it is almost never used to carry people. The four D-18T engines are 1980s high-bypass turbofans with 1980s fuel burn. The two auxiliary power units sit inside the main gear fairings and produce enough heat and blast that some airports require pavement protection before it starts them.

None of that matters when the alternative is not flying the cargo at all. It matters enormously when you are deciding whether to spend twenty billion euros designing a new one.

The restarts that never restarted

Production has been resumed on paper at least twice. In 2008 Russia and Ukraine agreed to build the aircraft jointly again, and at one point Russia looked likely to order twenty new airframes. That was shelved in August 2014 for reasons everyone can guess. In January 2019 Antonov announced it would restart production without Russian involvement.

No new An-124 has been delivered.

Meanwhile the fleet aged. Antonov Airlines flies five out of Leipzig/Halle with an average age just under thirty-seven years. One aircraft was destroyed on the ground at Hostomel in February 2022; five more Ukrainian machines sat out the invasion at Leipzig.

What a replacement would have to be

Any European successor has to clear a strange bar. It must be big enough to take loads an A400M cannot, which means a genuinely new aircraft. It must have both a nose door and a kneeling capability, or it loses the drive-through advantage that makes the An-124 useful rather than merely large. And it must be affordable enough to justify a production run that nobody can currently size, because the outsize charter market is measured in hundreds of flights a year, not thousands.

The An-225, the six-engined derivative built to carry the Buran shuttle, was the only aircraft that ever exceeded it. It was destroyed at Hostomel in 2022.

Which leaves Europe with the two options the EDA named last week: rebuild the Antonovs, or start drawing. Both take longer than the SALIS contract has left.

Sources: European Defence Agency; Antonov; declassified CIA assessments of Soviet airlift; Dennis Fricker, Flight International; Jane’s; NATO SALIS programme documentation; aeroTELEGRAPH.