This is the Antonov An-225 Mriya. The largest plane ever built. Here's some history and factual information.
It really is an amazing piece of human technology. Its first flight was on 21 December 1988 under the Soviet Union and it is still in use today as a commercial cargo plane (Antonov Airlines). It was originally designed to carry the Buran space shuttle and its rocket boosters. It takes a crew of 6 people to fly this plane. Wingspan: 88 meters (290 feet) Length: 84 meters (275 feet)
It can hold up to 300 000 kg of jet fuel; about 98,000 gallons. (Hope I did it right... jet fuel: 0.81 kg/L, 1L = 0.265 US gallons)
There is only one Antonov An-225 built, ever.. A second airframe was partially built; its completion was halted because of lack of funding and interest. This one was put in a storage hangar in 1994 as it was too expensive to fly. The six engines were removed and used in smaller An-124s. The An-225 was later re-engined (in 2000) and put back in service.
The 640-ton plane is powered by six Ivchenko Progress D-18T engines, giving the plane a combined maximum thrust of 140,580 kilogram-force; 309,930 pounds-force (1380 kilo-Newton). It has carried anything and everything; four military battle tanks (at once), wind turbine wings, parts of other planes, etc. Basically, anything too large for a normal cargo plane.
In 2000 the need for a second An-225 became apparent and Antonov Airlines (in Ukraine) started finishing the second one, which has been stored in its unfinished state since 1991. Due to various delays and financial reasons, they still haven't finished but they still plan on finishing a second one in the future. It is said to cost over $300 million and it will be able to hold 250 tonnes of cargo.