sentences:  This normally involves the replacement of glazed windows with opaque panels, the strengthening of the cabin floor and insertion of a broad top-hinged door in one side of the fuselage.Antonov An-225 "Mriya" and Antonov An-124 are the world's largest aircraft, used for transporting large shipments and oversized cargos.Usage of large military airplanes for commercial purposes, pioneered by Ukraine's Antonov Airlines in the 1990s, has allowed new types of cargo in aerial transportation.