The Antonov-225.
The A380 is currently the tallest flying aircraft, but in terms of wingspan and length, as well as overall cabin volume, the An-225 is larger. The An-225 also has a larger carrying capacity, by a long shot.
The An-225 is 84m long, with a wingspan of 88.4m with a payload of 250,000kg.
The A380 is 73m long with a wingspan of 79.8m with a maximum payload of 152,400kg (A380F).
For a good size comparison between the A380, An-225, 747-8, and the Spruce Goose, see the link below.
Source(s):
<a href='http://upload.wikimedia.org/wikipedia/commons/5/52/Giant_planes_comparison.svg'>http://upload.wikimedia.org</a>
