Relatives of the victims of a 1985 Japan Airlines jetliner crash commemorated on Saturday the 32nd anniversary of the world's deadliest single-aircraft accident that claimed the lives of 520 crew and passengers.

Relatives climbed to the Boeing 747's crash site on Osutaka Ridge in Gunma Prefecture, northwest of Tokyo, to mourn their loved ones lost in the accident.

"An aviation accident that claimed so many lives should not be forgotten," said Masato Sasaki, a 57-year-old doctor from Yatsushiro, Kumamoto Prefecture, who lost his uncle Yutaka Sasaki, co-pilot of the aircraft, in the accident.

Sasaki, who had not visited the site for about 30 years, said he apologized in front of grave markers for his long absence.

Masanori Takishita, 77, and wife Fumiyo, 74, from Tokyo, have been visiting the site since their second son Hiroshi was killed in the crash when he was just 11 years old.

Traveling alone, Hiroshi was on his way to visit relatives in Hyogo Prefecture, western Japan, after playing a baseball game.

"I want to see my grown-up son," Fumiyo said, as her last memory is of an 11-year-old boy who loved playing and watching baseball.

The couple cut down their visits to the site from three times a year to two times after Takishita had a stroke about five years ago. This would be their only visit this year.

"When I climbed the mountain and silently said 'I'm here,' I feel like Hiroshi is with us when we leave," Takishita said.

According to Japan Airlines Co., around 300 people from bereaved families climb the mountain on Aug. 12 every year to mourn their loss, with 2014 an exception due to bad weather. On the 30th anniversary in 2015, a record 406 people made the trek.

JAL President Yoshiharu Ueki climbed the trail and paid his respect to the victims while pledging air safety.

In the evening, a memorial ceremony will be held at "Irei no sono" (Memorial Garden) in the village of Ueno, with a moment of silence to be observed at 6:56 p.m., the time of the crash.

On Aug. 12, 1985, Flight 123, en route from Tokyo's Haneda to Osaka's Itami airport with 524 passengers and crew, crashed into the area, killing all but four aboard. A rupture in the plane's rear pressure bulkhead led to its vertical stabilizer being blown off, destroying its hydraulics and rendering it uncontrollable.

Among the dead in the accident which occurred during Japan's Bon summer holidays included 43-year-old singer Kyu Sakamoto, who is known for his hit song "Sukiyaki," as well as many families including children.

A Japanese government investigation commission in 1987 concluded that the accident was caused by improper repairs conducted by Boeing Co., the aircraft's manufacturer, on the pressure bulkhead with JAL failing to detect any problems in its maintenance checks.

Police referred to prosecutors 20 people including Boeing employees for their alleged negligence in 1988, but it was decided not to seek indictments after Boeing refused to cooperate.

Relatives commemorate victims on JAL jumbo crash anniversary