It was the kind of plane that seemed to fit the swinging go-go days with martini-swigging travelers lingering around a bar.

First-class passengers dressed in their Sunday best made their way up a spiral staircase to get to the “flying penthouse,” harking memories of private rail cars.

It seemed the epitome of plushness when it made its first commercial flight 40 years ago today. A Times reporter described the cabin as a “luxurious auditorium some genie had wafted aloft.”

Boeing Co.'s 747 was not only the biggest plane that anyone had ever seen before -- it was nearly three times larger than the largest jet flying at the time -- it transformed travel in a way that few have.

“It was marvelous,” said Marilyn Murphy, a former Pan Am “stewardess” -- the term for what are now “flight attendants” -- who flew on the 747 during its early years. “I always felt it revolutionized the way people travel because it became more of a social experience. People would congregate around the plane and talk about where they had been or where they were going.”

The plane was a game changer for Pan Am, which at the time was an international powerhouse but ceased operations in 1991. As soon as the airline received its first 747 in 1970, Chief Executive Juan Trippe switched the flight attendants’ uniforms, giving them a classier look with pristine white gloves and stylish blue hats.

“The plane ushered in a new era of luxury travel,” said Scott Hamilton, an aviation industry consultant in Issaquah, Wash. “It is truly an American icon. It was the first jumbo jet and a wonderful technical achievement.”

But when the first 747 rolled off the assembly line, the aircraft was so huge that some pilots refused to fly it and critics said it would never get off the ground. It almost bankrupted Boeing, and airport officials worried about how they would handle all the passengers.

Two generations later, the jumbo jet with its signature hump is still flying high and is one of the most recognizable planes in the world. Many of the 747 components were built in Southern California, including the 172-foot-long center fuselage in Hawthorne.

History books say the plane made its first commercial flight on Jan. 21, 1970, but the Pan Am flight actually took off from New York’s John F. Kennedy International Airport bound for London’s Heathrow Airport at 1:52 a.m. Jan. 22 because of a 6ÃÂÃÅ 1/2ÃÂÃÂ§-hour delay.

Four decades later, the 747 is still a common sight at Los Angeles International Airport, where dozens of the latest generation of the mammoth plane carry thousands of passengers to far-flung destinations in Asia and Europe each day.

Two years ago, the 747 was dethroned as the world’s largest passenger jet when the double-decked Airbus A380 entered service with Singapore Airlines.

Boeing built more than 1,400 747s, making it one of the most successful commercial jetliners ever.

Air Force One, a modified 747, continues to be a symbol of U.S. might. And NASA still uses a 747 to transport space shuttles back to Florida whenever they land at Edwards Air Force Base in the Mojave Desert.

But things weren’t always so rosy for the 747. When the program was undertaken, Boeing didn’t have the financial strength or the manufacturing capability to produce them. The company went deep into debt and had to strike deals with suppliers to make the parts on their own dime.

“It was really a critical time for Boeing,” Joe Sutter, chief engineer on the 747, said in an interview. “There came a time when the banks didn’t want to lend us any more money. So, by going after the 747, the company was essentially committing the entire company.”

It didn’t get any easier as the program went forward. The airplane was overweight and the new engines had overheating problems.

“We knew we’d have a good flying machine once we worked the kinks out,” Sutter said. “It was make or break for the company.”

The 747’s cavernous cabin, which was built in Hawthorne, changed travelers’ flying experiences. Before the 747, traveling on a jetliner was like flying in a cramped metal tube.

The change was dramatic. The 747, with its five cabin sections and twin aisles, stretched nearly the length of a football field. It could carry more than twice as many passengers as existing commercial planes, and amenities such as multiple movie screens and snack bars seemed to make flying more enjoyable.

“Flying in a 747 is more like flying in a room with high ceilings than anything else,” Hamilton said.

To this day, the Hawthorne factory ships fuselage panels -- now for the forthcoming variant, the 747-8 -- to Boeing’s assembly plant in Everett, Wash., by rail.

The site, currently operated by Vought Aircraft Industries Inc., has produced the fuselage panels for every 747 that has taken to the skies -- including Air Force One -- since the aircraft program began in 1966.

“A tremendous amount of people in this area can attribute their jobs to the 747,” said Dana Dickson, the site’s general manager. “There have been quite a few father-and-son teams that have worked on the program.”

Twice a week, Vought packages the parts and sends them along to Boeing in three custom, oversized rail cars. For the most part, the arrangement has worked without a hitch, Dickson said. But in the 40-year partnership, there have been a few hiccups. One of them was the Mt. St. Helens eruption in Washington in 1980.

“We were at peak production around that time, so it ÃÂsreally made things difficult,” Dickson said. “There were about 2 or 3 inches of volcanic ash on the tracks. So, everything had to be cleaned up, and we had to put special packaging on the product. It was just a wild time.”

The Hawthorne site is only five miles east of LAX. Every day, the 1,100 people who work at the plant can see the fruits of their labor. LAX has more 747 passenger flights than any other airport in the country.

“Every now and then you’ll hear one of the workers say, ‘There goes the jewel in the sky,'ÃÂ|" said Reggie Morris, a Vought aircraft mechanic who has worked there for 35 years. “Without looking, I know that the 747 is flying by. There’s a lot of pride and integrity that comes with that.”

william.hennigan@ latimes.com