TOKYO -- In August 1985, a few minutes into a Japan Airlines flight from Tokyo to Osaka, Japan, a bulkhead in the rear of the Boeing 747 ruptured with a bang, releasing a blast of pressurized air from the cabin that blew apart the plane's tail fin and severed its hydraulic plumbing.

The stricken jet rolled and yawed. As passengers cried out and a cloud of condensation filled the windy cabin, Hirotsugu Kawaguchi, a 52-year-old shipping-company executive in seat 22H, took out his black pocket diary and scrawled a message to his family across seven pages.

"Be good to each other and work hard. Help your mother," he exhorted his son and two daughters. "I'm very sad, but I'm sure I won't make it ... . I don't want to take any more planes. Please God, help me. To think that our dinner last night was the last time."

After an excruciating 32-minute slalom in the sky, the jetliner plowed into a pine-covered mountain west of Tokyo, killing 520 passengers and crew and leaving four survivors. The crash remains the worst single-aircraft accident in history. It traumatized the country, and JAL, the national flag carrier, has struggled ever since to atone for the disaster and restore its reputation for safety.

Now, dogged by a recent string of publicized safety lapses, JAL has exhumed its worst memory and opened a museum filled with mementos like Mr. Kawaguchi's diary. The exhibition includes crumpled passenger seats, the reassembled fragments of a tail fin and fuselage, and other wreckage from the crash. The purpose of it all is to drive home the importance of safety to the airline's 42,000 employees, and show the public that JAL is serious about this commitment.

The Safety Promotion Center, at Tokyo's Haneda Airport, is an extraordinary undertaking for an airline. To publicly display such shortcomings, let alone the poignant but grisly evidence of a disaster two decades old, is unheard of in an industry whose players are hypersensitive about their reputations for safety.

"I can't see many other airlines, if any, willing to take such a bold and imaginative step as JAL has just done," said John Bailey of Icon Communications, a Singapore consultancy in crisis communications for airlines. "I don't think it would have occurred to me to advise them to do that."

The center, which opened in April, features explanatory videos in Japanese and English and a library on aviation safety. JAL is requiring most of its staff to visit. On a recent day, Shuhei Fukasawa, a JAL parts-purchasing manager, and Naka Iwamoto, who handles the needs of handicapped passengers, were two of the employees in attendance.

"This is, I think, a sacred place for everyone at Japan Airlines to learn safety as a priority," said Mr. Fukasawa, who was making his first tour of the facility.

For Ms. Iwamoto, who at 28 barely remembers the crash, a display of three mangled seats, one with a torn but still buckled seat belt, was the center's most disturbing exhibit.

Then there are the notes, from Mr. Kawaguchi and four other passengers, which were added to the exhibit earlier this month. "Bang, we're starting to fall. Be brave and live," Keiichi Matsumoto, in seat 20H, wrote to his wife and son, his words racing across the pages of a blood-smeared notebook.

The museum's centerpiece is the 747's rear bulkhead, a row of rivet holes testifying to a flawed splice made by Boeing Co. seven years before the crash that U.S. and Japanese crash investigators concluded was its probable cause. On the day of the accident, Aug. 12, 1985, the brittle splice broke apart, and the bulkhead -- a convex partition between the pressurized cabin and the unpressurized tail section -- peeled open "like a tangerine," according to one Japanese investigator.

Boeing and JAL both paid undisclosed financial settlements to each victim's family. A JAL official said Boeing paid the lion's share, but he didn't specify. Boeing, which wouldn't comment on the payment breakdown, said it acknowledged the faulty repair and made changes in its maintenance and design practices. It rerouted the 747's hydraulic lines, for example, to prevent a total loss of control.

In a culture famous for ritualizing contrition, JAL executives note that the airline itself failed to detect the defective repair and put people at risk by continuing to fly the plane.

"To the passengers and society, this is Japan Airlines' accident," said Toshiyuki Shinmachi, JAL's current chairman.

Yutaka Kanasaki, the center's director, says the museum has as many as 100 visitors a day. Some of them have no connection to JAL or the crash. Bicycle postwoman Yuko Matsumoto made a two-hour trip from the city of Fujisawa to visit. She hadn't made an appointment the previous day, as the museum requires. And she looked out of place with her fanny pack and sneakers. Even so, the 38-year-old Ms. Matsumoto was able to attach herself to a group of JAL employees taking a guided tour. She lingered long after the tour ended and studied each display.

Some visitors to the center are relatives of the dead. Kuniko Miyajima, who lost her 9-year-old son, Ken, in the crash, heads a network of victims' relatives called the 8.12 Association. She has been to the safety-promotion center and thinks it is a good idea. "I believe that most of the bereaved families are happy about it, too," she said in an interview in Tokyo.

Mariko Kawaguchi, whose father wrote the seven-page farewell displayed at the center, and who has yet to go there, said she appreciates JAL's motives but hopes the company doesn't treat the museum as an end in itself. "This is not the end of the safety effort," she says. "This should be the start."

In just the past year, tires burst on the front wheels of a JAL plane as it landed, a JAL pilot tried to take off without approval from air-traffic controllers, and an engine on a subsidiary carrier's jet caught fire after takeoff.

Japanese broadcasters, with news crews based at the country's major airports, have been quick to pounce on every lapse, large and small. Passengers, alarmed at the stream of negative reports about safety at JAL, began to desert the carrier for rival All Nippon Airways. The exodus contributed to a loss of $403 million at JAL in its latest fiscal year.

Japan's Civil Aviation Bureau scolded JAL for the lapses, and the Ministry of Land, Infrastructure and Transport proposed in June 2005, that the airline set up a panel of outside experts to advise it on safety. The panel's members -- a journalist and four professors -- recommended 37 measures in December, including the creation of a "safety-documentation center."

In May of last year, Mr. Shinmachi, then serving as JAL's president and chief executive, had separately conceived of a museum-like exhibit of the debris to promote safety. After many "difficult" internal debates "from the top of the management down to the staff," Mr. Shinmachi said, he began to win over the skeptics, with crucial support from several activists among families of the crash victims.

"What I have been wishing for the past 21 years is to make some use of those 520 lives, including my son's," said Ms. Miyajima of the 8.12 Association. "Keeping the debris and making it public is the first step toward preserving what happened forever."

Ms. Miyajima recalls the crash site, on Mount Osutaka, or Hawk's Nest Mountain, as "a picture of hell." She climbed up there from a staging area three days after the accident to search for Ken, who had been traveling alone for the first time.

Today, markers erected on the mountain in memory of the dead are adorned with flowers and mementos, including bottles of whiskey and a rusty fishing rod. At Ken Miyajima's marker lies a veritable toy chest of trains, cars, a spinning top, a camera and a baseball.

"He was our youngest child," said his mother, "and a little bit spoiled."