Worlds largest aircraft.

It's not the first time the Chinese have bought an aircraft from Russia/Ukraine and "reverse engineered" to their specifications. Many of the designs came from the Antonov,Tupolev and Ilyushin design bureaus, and it some cases the Chinese made it better by using some Western technology(engines in particular). Another thing to remember is that a lot of the designs originally had military purposes in mind(the Antonov 124 Ruslan NATO code name: Condor was designed to be a strategic military airlifter to haul tanks, troops or other items in the event of war). With the end of the Cold War this aircraft found a new lease on life, flying oversize or heavy items that would otherwise have to be shipped by land or sea. Basically the plane found itself in a niche market, with little or no competition.