Near the front of the seated audience was Joe Sutter, Boeing's chief engineer on the original jumbo, and known as the "father of the 747."
The plane itself, unveiled from behind an enormous curtain to rapturous, thudding music, was bright red and white - a departure from Boeing's recent blue - bearing generic Boeing livery on the side and '747' on its orange tail.
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 69-meter wingspan, took the world's breath away on a sunny morning at Everett in September 1968.
"People were awe-struck. It was a monster, nobody had seen anything like it," said Jim Mullins, a writer who covered the original rollout for King Broadcasting.
"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 plane to the 525-seat Airbus A380 when it was unveiled in 2005.