WARSAW—Polish military prosecutors on Friday charged Polish and Russian officials with causing an airplane crash that killed President Lech Kaczynski and 95 others in 2010, while admitting the crew of the plane was mainly to blame.

The investigators broadly confirmed earlier findings by the Polish administration concluding that bad weather, mistakes by the Polish Air Force detachment in charge of transporting the president, and errors by Russian air-traffic controllers all contributed to the accident.

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