Boeing 747-400BCF Freighter

A Thai Airways Boeing 747-400BCF converted freighter.

A Thai Airways Cargo 747-400BCF - a Boeing Converted Freighter, originally built as a passenger aircraft and rebuilt for cargo.

Conversion is what kept 747s earning long after airlines stopped flying them with seats: the airframes were sound, and freight cares about volume rather than cabin comfort. More on the 747-400BCF.