Wichita ? Crowds lined up Friday to see a 50-year-old fighter that some say still has its best years ahead.

The B-52 Stratofortress, America’s longest-lived bomber, celebrated its 50th birthday with a few thousand of the men and women who designed, built and modified the flying fortress.

Crowds waited at the Boeing factory to climb on catwalks set up to let them peer inside the cockpit of the last B-52H built.

And they cheered as another of the big gray bombers executed a low altitude fly-by just east of the factory.

It was the anniversary of the first flight of a YB-52, which first lifted off on April 15, 1952, at Boeing Field in Seattle.

“Back in 1952, no one dreamed the B-52 would be in the war plan for the year 2042,” said Guy Townsend, a retired Air Force brigadier general and Boeing Co. retiree who flew most of those early flights.

The year 2042 is when the aircraft is scheduled to be phased out, said Scot Oathout, Boeing’s B-52 project manager. He said plenty of work remains to be done at Boeing to keep the B-52 part of the arsenal, but he saluted those who take that challenge eagerly.

“If you thought the first 50 years were impressive, you ain’t seen nothing yet,” Oathout said to a round of applause.

The B-52 was conceived in 1946 as America’s next-generation bomber to replace the B-47. The plane was designed as a strategic intercontinental bomber, to carry nuclear weapons in the event the Cold War turned hot, Oathout said, but its role was modified to add conventional bombing during the Vietnam War, the Gulf War and, now, the war on terrorism.

“She’s a tough one, and we’re real proud of our capabilities to drop ’em in close now,” said Bob Shaw, an avionics engineer at Boeing who has worked on updating electronics systems on the B-52 since 1976.

From the time the prototype, the XB-52, rolled out in November 1951, until production ended in Wichita on June 22, 1962, a total of 744 B-52s were produced. Wichita built 467.

Today, the Air Force still flies 94 B-52H models, and NASA uses another pair of the planes. Both of the NASA planes were on display Friday at Boeing.

What made the B-52 survive so long in a military where weapons systems are changed out so frequently?

“Excellent maintenance, great design, great support from Boeing, and from the Oklahoma City Logistics Center,” said Lt. Col. Harry Bender, pilot of the B-52H on display.

“We all grew up flying this airplane,” he said. “She has taken good care of us.”