The U.S. government divulged to an influential American newspaper crucial information on improper repair work on a plane carried out by Boeing Co., suggesting it was the presumable cause of the 1985 crash of a Japan Airlines jet, after sensing reluctance by Japanese authorities to release the data, former U.S. officials have told Kyodo News.

Japanese aviation authorities were thought to be hesitant about disclosing the information on the botched repair because that could impact law-enforcement investigations conducted separately to see if there was any negligence in Boeing's servicing the plane or in the subsequent inspections done by Japan Airlines or the Transport Ministry.

On Aug. 12, 30 years will have passed since Flight 123, a packed jumbo jet bound for Osaka, crashed into a mountain in Gunma Prefecture about 40 minutes after taking off from Tokyo, killing 520 passengers and crew members. Four female passengers miraculously survived.