[2] The series was based on the Russky Vityaz or Le Grand, the world's first four-engined aircraft, designed by Igor Sikorsky.

[3] The Ilya Muromets aircraft as it appeared in 1913 was a revolutionary design, intended for commercial service with its spacious fuselage incorporating a passenger saloon and washroom on board.

[7] It was based on his earlier S-21 Russky Vityaz, which started out as the twin-engined Le Grand, then as the twin tandem-engined Bolshoi Baltisky before placing all four of the Baltisky's engines in a tractor configuration along the lower wing's leading edge to create the Russky Vityaz — which had played an important role in the development of Russian aviation and the multi-engine aircraft industries of the world.

Lighting was provided by a wind-driven generator and heating was supplied by two long engine exhaust pipes that passed through the corners of the cabin.

[11][12] From 30 June to 12 July 1914, it set a world record by making a trip from Saint Petersburg to Kiev, a distance of some 1200 km, and back.

The Army placed an order for ten four-engined airplanes of the Ilia Mourometz type and the factory personnel was overjoyed by this final approval of the results of two years of hard work.

"[14] The acclaim received by Sikorsky included Tsar Nicholas II presenting him with the Order of St. Vladimir, Fourth Degree, arranging for an exemption from the wartime draft to allow him to continue his design work, and a promise of a grant worth 100,000 rubles from the State Duma.

Internal racks carried up to 800 kg of bombs, and positions for up to nine machine guns were added for self-defense in various locations, including the extreme tail.

[23] German Fighter Pilots often were reluctant to attack Ilya Muromets in the air due to their defensive firepower including the unique tail gun position, and the difficulty in bringing down such a large aircraft.

[24] On 12 September 1916 (Julian calendar), the Russians lost their first Ilya Muromets in a fight with four German Albatros, three of which it managed to shoot down.

By 1917, attrition from constant flying had reduced the bombing fleet substantially and only four bombers remained at the front line; the other Ilya Muromets were relegated to trainer duties.

[28] A few remaining aircraft were used by the newly formed Soviet Air Forces during the Russian Civil War as trainers and transports.