The Muromets did not appear from nothing. In 1913 Igor Sikorsky, still only in his mid-twenties and working as chief designer at the aviation department of the Russo-Baltic Wagon Factory, built the Russky Vityaz — a biplane so large that it was initially flown with two engines and then rebuilt with four. It is generally credited as the world’s first four-engine aircraft, and its success settled a live and genuinely serious argument of the day.

That argument mattered because the prevailing expert opinion held that multiple engines were a dead end: that an engine failure on one side would produce uncontrollable asymmetric thrust, and that the weight and drag of extra engines and structure would swallow any gain. Sikorsky is said to have answered the doubters partly by demonstration — famously walking out onto the lower wing in flight to show how steady the big machine remained — and partly by simply flying the aircraft, repeatedly and safely, in front of witnesses.

From the Vityaz, Sikorsky quickly developed a refined and enlarged design: the S-22 Ilya Muromets. It kept the four-engine layout but added a fully enclosed fuselage cabin, greater span and much greater load capacity. The prototype flew around the winter of 1913–1914 and immediately began setting records. Where the Vityaz had proved the concept, the Muromets turned it into a practical, capable aircraft.

Why it mattered

Every heavy bomber, airliner and long-range multi-engine aircraft that followed — from the Handley Page and Gotha bombers of the same war to the great flying boats and airliners of the 1920s and 1930s — built on the idea the Vityaz and Muromets proved first: that you could hang several engines on one big airframe, carry a genuinely useful load, and fly a long way safely and repeatably. It is difficult to name a more consequential idea in the first two decades of powered flight.

What made the early Muromets so startling was not just its size but its comfort. By the surviving accounts it offered an enclosed, heated passenger cabin — warmed using engine exhaust gases — with electric lighting powered by a wind-driven generator, upholstered seating, a table, large windows, and a small private washroom. Some descriptions add a separate sleeping compartment and an external promenade or observation area where passengers could step out in flight. For 1913, when virtually every other aircraft in the world was an open-cockpit, single- or two-seat machine, this was close to science fiction made real.

The comfort was not an indulgence for its own sake; it was an argument. Sikorsky was trying to show that aviation could be a serious, civilised means of transport — safe and comfortable enough for ordinary passengers — rather than a fairground thrill or a soldier’s gamble. He used the aircraft to set records that were as much about publicity as engineering: carrying large numbers of passengers, climbing to notable altitudes, and flying long distances such as the St Petersburg–Kiev round trip of 1914.

When war came in August 1914, all of that comfort was stripped out or repurposed. The spacious cabin that had carried well-dressed passengers now carried bomb racks, extra fuel, a crew of several men and their machine guns. The airliner became a warplane almost overnight. It is an unusually direct example of a civil design being pressed into military service — and, awkwardly for a peaceful vision, the very qualities that made it a fine airliner made it an effective bomber. The dream of comfortable passenger flight would have to wait; the Muromets went to war instead.

In December 1914, on the initiative of Mikhail Shidlovsky, Russia grouped its Ilya Muromets bombers into a single dedicated formation: the Eskadra Vozdushnykh Korablei, the “Squadron of Flying Ships”. Each aircraft was treated almost like a naval vessel, with its own name and number and a captain in command, and the whole unit had its own bases, workshops, training and command structure. This is why the type is so often described as the world’s first strategic bombing unit.

That claim is reasonable, but — like many aviation “firsts” — it deserves a careful hedge. Other nations were developing bombing aircraft and bombing forces in the same period, and definitions of what counts as a “strategic” or “heavy” bomber unit differ. What is not seriously disputed is that the EVK was among the earliest formations built specifically around large, multi-engine bombers, and that it worked out much of the practical doctrine of heavy bombing before anyone else had a comparable force in the field.

From 1915 the EVK flew long-range bombing and reconnaissance missions against German and Austro-Hungarian rail junctions, supply dumps, bridges and troop concentrations across the Eastern Front. Over the war the squadron is commonly credited with more than 400 sorties and roughly 65 tonnes of bombs dropped. Those numbers are modest by the standards of the next war, but as pioneering work — in navigation, bomb-aiming, aerial photography and defensive gunnery — they were anything but trivial.

Why it mattered

The EVK was the laboratory in which the practical craft of heavy bombing was invented: crew roles, defensive gun positions, formation flying, target navigation and reconnaissance photography. The strategic results on the Eastern Front were limited, but the organisational template — a dedicated heavy-bomber unit, run like a fleet — is one every later air force would recognise.

Honest answer first: reliable unit-cost and cost-per-flight-hour figures for the Ilya Muromets simply are not recorded in any way that compares to a modern aircraft. It was built in small numbers, under wartime conditions, in a currency and economy — the Imperial Russian rouble on the eve of revolution and then hyperinflation — that make any single price figure essentially meaningless. So in the specification tables below, the cost rows read “not reliably recorded (WWI)” rather than a made-up number dressed up as fact. That is the honest position, and we would rather state it plainly than invent false precision.

What can be said is qualitative. The Muromets was expensive by the standards of its time and place — a large, complex, four-engine machine built by a country whose industry struggled to produce reliable aero-engines at all. The real recurring “cost” of the programme was often measured not in roubles but in engines: good powerplants were scarce, frequently imported, and the single most important limiting factor on how many aircraft could fly and how well they performed.

That scarcity, as much as enemy action, shaped the type’s entire career. When you read that “around eighty” were built over four years, it is worth remembering that keeping even a fraction of them simultaneously serviceable, engined, armed and crewed was a continual struggle — and that the true cost of a strategic bomber in 1915 was as much organisational and industrial as it was financial.

For readers who care about the economics of flight, this is exactly why comparing a WWI pioneer to a modern jet on a “cost per hour” basis breaks down: the categories that make such comparisons meaningful — a stable currency, a functioning market, standardised production, recorded fleet flight hours — largely did not exist for the Muromets. The comparison tool that accompanies this museum will always show this aircraft’s cost fields as unrecorded, and that is the correct answer.

The single most surprising fact about the Ilya Muromets — that across the whole war only one is generally recorded as lost to enemy fighters in air combat — is not luck. It follows directly from how the aircraft was built and armed. Understanding it is the key to understanding why a slow, enormous 1915 biplane was not the easy target it looks.

Start with the structure. The Muromets was large and strongly built, with multiple spars and a great deal of redundant wooden structure. It could absorb a lot of damage — holes in the fabric, hits to the structure, even the loss of an engine — and keep flying. A single-seat fighter’s rifle-calibre machine guns, firing at a fast-moving deflection angle, often simply could not do enough damage quickly enough to bring it down.

Then add the guns. The Muromets could carry several machine guns covering a wide arc, including dorsal and rearward positions that were genuinely dangerous for an attacking fighter to approach. A fighter trying to close on the tail of a Muromets was flying into the muzzles of defensive guns manned by crew who had room to move, aim and reload — a very different proposition from attacking a lone two-seater. On 12 September 1916, the one Muromets caught and downed by fighters is commonly credited with shooting down three of its four attackers first, which tells you how costly it was to engage.

Why it mattered

This is, in embryo, the whole logic of the heavy bomber that would dominate the next thirty years: a large, robust, self-defending aircraft that flies into hostile skies and relies on structure and massed defensive fire to survive. The Muromets got there first, and its survival record was the proof of concept.

It is easy, with an aircraft this pioneering, to slide from admiration into exaggeration. So it is worth setting out plainly what the Muromets did and did not do. What it did: it was generally the first four-engine aircraft to enter series production; it began as a genuinely revolutionary passenger aircraft; it became the core of what is often called the first heavy-bomber unit; and it flew hundreds of combat sorties with a survivability that was extraordinary for its day.

What it did not do: it did not win the war, or come close. The bombing effort was small in scale and limited in strategic effect. It did not exist in large numbers — only a fraction of the roughly eighty built were operational at any time. And it did not have a long career; obsolete within a decade, worn out and under-engined, it was quietly retired in the early 1920s.

None of that diminishes it. Firsts are, almost by definition, modest in raw achievement and enormous in influence, because their real product is a proven idea rather than a decisive result. The Muromets proved that a large multi-engine aircraft could carry a serious load a long way, defend itself and come home — and that idea, once proven, never went away. It runs straight through the bombers and airliners of the century that followed, which is why a slow Russian biplane from 1913 still matters.

The Ilya Muromets was not one aeroplane but a family, developed continuously from 1913 to 1918. The earliest passenger and reconnaissance machines (the S-22 series) gave way to progressively larger, stronger and better-armed bombers as wartime experience accumulated. Later types — commonly labelled with Cyrillic-derived letters such as the “Veh” (V) and “Yeh” (E) series, and running through designations up to the S-25 — introduced revised noses, more powerful or more numerous defensive guns, strengthened structures and different engine fits.

The general trend across the family is easy to summarise even if the details are messy: from comfortable pre-war airliner toward purpose-built wartime bomber, with each iteration a little more warlike than the last. Noses were reshaped for better fields of fire and bombing; gun positions multiplied; loads crept upward where engines allowed.

Because the changes were incremental, overlapping and often applied to existing airframes, and because the records are incomplete and sometimes contradictory, sources genuinely disagree on exactly how to divide the type into distinct variants and how many of each were built. The sensible approach — and the one taken here — is to treat the variant boundaries as approximate rather than to pretend a false precision the evidence does not support.

No single engine defines the Muromets, and that is central to understanding it. Over its life the type flew behind German Argus and Mercedes engines, British Sunbeam and other imported units, French Renaults, and Russian-built RBVZ-6 engines — sometimes in mixed installations, with different engines on the inner and outer positions of the same aircraft.

The outbreak of war in 1914 made a difficult situation acute. It cut Russia off from German engines overnight — the very engines several Muromets had been designed around — and strained the supply of everything else, from imported units held up by blockade and shipping shortages to domestically built engines that Russia’s industry struggled to produce in quantity or to a consistent standard.

This is the honest heart of the Muromets story: the airframe was ahead of the engines available to power it. The performance figures quoted for the type vary so widely between examples largely because the engines varied so widely, and the number of aircraft operational at any one time was often set not by how many airframes existed but by how many could be given four reliable, running engines. It is not an exciting fact, but it explains more about the type’s real-world career than any tale of combat.

At least one Ilya Muromets was built or converted as a floatplane, trading its wheeled undercarriage for large floats so that it could operate from water. In that configuration it was, for a time, among the largest seaplanes anywhere in the world — a striking sight, and a logical experiment for a nation with long coastlines and rivers and a serious naval-aviation interest.

Operating so heavy an aircraft from water brought its own problems, from the drag and weight of the floats to the difficulty of getting a fully loaded machine unstuck from the surface, and the floatplane remained a small side-branch of the Muromets story rather than a mass-produced type.

But it is worth mentioning, because it shows how far Sikorsky and the R-BVZ team were willing to push the basic design, and how versatile the underlying concept was. The same big, strong, multi-engine airframe that made a good bomber could be adapted toward passenger transport, reconnaissance and maritime work — a flexibility that would become a hallmark of large aircraft in the decades that followed.

The total number of Ilya Muromets built is usually given as around eighty, with individual sources ranging from roughly 76 to 83. As always with the type, the honest figure is a range rather than a single confident number, and only a fraction of those built were ever serviceable at any one moment, given the chronic engine shortage.

Combat losses to enemy fighters are commonly recorded as a single aircraft across the entire war — a figure so striking that it needs to be stated carefully to avoid being misunderstood. It refers specifically to Muromets lost in air combat to enemy aircraft. It does not mean only one Muromets was ever lost; the type also suffered losses to accidents, to anti-aircraft fire, to engine failures and forced landings, and to the general wear, disorganisation and destruction of the revolutionary period.

Read correctly, though, that single air-combat loss is still remarkable. It says that in the specific, dangerous business of being hunted and attacked by enemy fighters — the fate that destroyed so many aircraft of the period — the Muromets was, for its era, almost uniquely survivable. That is the fact worth carrying away from the numbers, provided it is not stretched into the claim that the aircraft was somehow invulnerable, which it plainly was not.