governments. The Germans tried to copy its design, using the fragments of the Ilya Muromets they had shot down over their territory in September 1916. By the end of 1916, the design was generally believed to be at the end of its development cycle, with ensuing modifications to individual aircraft, such as additional armor and weapons, making the aircraft too heavy and not suitable for operational use. Continual changes in the field as well as the factory led to many aircraft being redesignated as a new variant. Further designs based on the original Ilya Muromets bombers included a more dedicated attack version. Russian Revolution and aftermath Following the February Revolution of 1917, the Ilya Muromets bombers continued to fly with the Russian Imperial Army but others were seized by the provisional government with pilots also defecting to the Ukrainian squadron of Hetman and General Pavlo Skoropadsky, with at least one Ilya Muromets being flown by Polish forces. The remainder of the aircraft flew with the Red Army until mid-1919. The Ilya Muromets continued in production after the war, with only a handful being finished. From May–October 1921, the aircraft was utilized in its originally intended role of passenger transport on the Moscow-Kharkov line; six saw service as a civilian passenger airliner and mail plane. After carrying 60 passengers and two tons of freight, the Ilya Muromets were considered too difficult to maintain as engines and airframes were worn out and on 10 October 1922, the airliners were retired. The last flight of an Ilya Muromets bomber took place in 1922 at the Air Shooting and Bomb-dropping School in Serpukhov. Variants Ilya Muromets No. 107 Experimental airliner, 1913; fitted with four Argus As I engines, later refitted with two Salmson 2M7 and two Argus 115 hp engines. Ilya Muromets No. 107 Hydroplane Hydroplane modification of airframe No. 107, fitted with two Salmson 2M7 and two Argus 115 hp engines. Ilya Muromets Kievsky No. 128 Experimental airliner, 1914; fitted with two Argus 140 hp engines and two Argus 125 hp engines. Ilya Muromets S-22 Type A Unarmed trainer, one built 1913, used in Gachina Air School in 1914 Ilya Muromets S-23 Type B(eh) Bomber Bomber. First flight: 1914, in service August 1914, original armament: one 37mm cannon, one 8 mm machine gun; six built (heavily modified). Type B No 135, 1914; fitted with four Argus engines of 130 hp each. Type B