Next month marks three years since a China Eastern jet plunged into a hillside, killing 132 people, with relatives still waiting to learn what caused China¡¯s deadliest air disaster in three decades.

It is one of dozens of accidents worldwide in which investigators have yet to issue a final report designed to help prevent new accidents, despite a target of one year.

While recent deadly crashes in Kazakhstan, South Korea and the United States and the non-fatal flip of a crash-landed jet in Canada have thrust safety into the spotlight, the industry is worried that too many past accidents remain unresolved.