The unveiling came almost 42 years to the day since the maiden flight of the 747, which went on to become the world's most recognized jetliner and transformed the global travel industry.
It is the first appearance of a radically new version of the passenger jet since the first jumbo, with its humped two-storey cabin and 196-foot (69-meter) wingspan, took the world's breath away on a sunny morning at Everett in September 1968.
"Today it looks ordinary, but at that time there were no airplanes even close to it in size. They opened up the hangar doors and it was just unbelievable. People reacted as if they were rolling out the Empire State Building."
The 747 lost its crown as the world's largest airliner when the 525-seat Airbus (EAD.PA) A380 was unveiled in 2005. But at 19 feet longer than its predecessors, this one will be the longest.
It is the first time the 747 fuselage has been stretched to make the biggest passenger jet marketed by a U.S. manufacturer.
The 747-8 -- listed at $317.5 million -- also boasts new wings, a new tail, state-of-the-art engines and a new cockpit, making it, according to specialist magazine Flight International, "unrecognizable from that first jumbo jetliner."