Relatives on Monday prayed for the victims of the 1985 Japan Airlines jumbo jet crash, the 34th anniversary of the world’s deadliest single-aircraft accident.

A ceremony was held in the evening in the village of Ueno, at the foot of the Osutaka Ridge in Gunma Prefecture, where the plane went down. A total of 520 people out of the 524 aboard were killed.

The relatives offered silent prayers at 6:56 p.m., the time of the crash, after climbing the steep mountain trail to grave markers and a monument at the crash site to mourn their loved ones.

Concerns over air safety have increased recently following a series of alcohol-related incidents at domestic airlines, including JAL, such as higher-than-permissible limits of alcohol being detected in preflight tests for flight crew.

“People may think, ‘What is JAL doing? Did it forget the crash?'” Yuji Akasaka, president of Japan Airlines Co., told reporters after offering flowers at the monument. “I felt guilty while I was climbing the mountain. We will strengthen our efforts to change our crew members’ mindset.”

JAL should “look back to the memories and lessons of the accident,” said Masayoshi Yamamoto, 39, who lost his 49-year-old father, Kenji, in the accident.

Toru Izutani, 60, said he came to the venue to tell his younger sister, who died in the crash age 20, that his grandchild was born in May.

“I have lived the best I can for my sister,” he said.

On Aug. 12, 1985, JAL Flight 123, a packed Boeing 747 en route from Tokyo to Osaka during the Bon summer holiday season, crashed about 40 minutes after taking off.

The crash claimed the lives of all but four of the 524 crew members and passengers on board, many of whom were on their way home to see their families.

In 1987, a government investigation commission concluded that the accident was caused by improper repairs conducted by Boeing Co. on the plane’s rear pressure bulkhead, the rupture of which blew off the craft’s vertical stabilizer and destroyed its hydraulics.