UENO, Gunma Pref. -- Kin marked the 20th year Friday since 520 of their loved-ones died when a Japan Airlines jumbo jet crashed on a mountain in Gunma Prefecture -- the worst single-air craft accident in aviation history.

Dozens of relatives of the victims climbed the steep slop in the rain to the crash site to clear the weeds around a memorial stone and place flowers before a monument located on Osutaka Ridge, where all but four people on board perished.

JAL President Toshiyuki Shinmachi also climbed the mountain -- the first time in eight years that a JAL president has done so on the anniversary -- to pay his respects and pledge greater safety efforts. JAL, however, has been beset with a spate of scares and safety blunders involving its aircraft this year.