Stratolaunch. The aircraft with the longest wingspan at 117m is the Stratolaunch. The Stratolaunch is a special plane (or a pair of planes) built to deliver payloads, such as satellites, into spatial orbits. It weights a hefty 226,796 kg without payload.
Hughes H-4 Hercules. At second, is a prototype strategic airlift flying boat built by the Hughes Aircraft Company - the Hughes H-4 Hercules (a.k.a Spruse Goose). Built in 1947 and the only of its kind built, with a cost of $2.5 million dollars, the Hughes H-4 Hercules has a wingspan of 98m.
Antonov An-225 Mriya. In third place, with a wingspan of 88m, is the heaviest plane on Earth - the Antonov An-225 Mriya of Ukraine. It was originally built for military transport purposes, but today, it is primarily deployed for commercial cargo transport.
Datasets on Aircrafts:
Most expensive plans in the world
Tallest planes ranked by height
Planes with the longest wingspans
Heaviest aircrafts in the world - unloaded weight
Largest cargo planes in the world
Passenger aircrafts with highest maximum seating capacities