Relatives of the victims of a 1985 Japan Airlines jumbo jet crash marked the 33rd anniversary on Sunday of the world's deadliest single-aircraft accident that claimed the lives of 520 crew and passengers.

As in past years, relatives climbed the steep mountain trail to the Boeing 747 crash site on Osutaka Ridge in Gunma Prefecture, northwest of Tokyo, to mourn their loved ones lost in the disaster.

Kimiko Yoshida, 84, who lost her daughter in the accident, said, "She is always on my mind, but I feel like I can get close to her every time I come here on Aug. 12."

The relatives also prayed for aviation safety, just days after a rescue helicopter crashed in the mountains in Gunma Prefecture, killing all nine people aboard.

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.

A Japanese government investigation commission in 1987 concluded that the accident was caused by faulty repairs conducted by Boeing Co., the aircraft's manufacturer, on the pressure bulkhead in 1978, with JAL failing to detect any problems in its maintenance checks.

Japanese police referred to prosecutors a total of 20 people including Boeing and JAL employees for their alleged negligence in 1988. But none were indicted after Boeing refused to cooperate.

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.