On April 26, 1986, an accident rocked the No. 4 reactor at the Chernobyl Nuclear plant in the Ukrainian SSR, beginning the worst nuclear accident in human history. In the aftermath of the explosion, thousands of aircraft and other vehicles were used to survey the area, then to remove radioactive debris. As a result, these vehicles (not to mention the people operating them...) became radioactive themselves, and were left behind in the Chernobyl Exclusion Zone.
Despite being guarded, and located in an area expected to be uninhabitable for 300 to 30,000 years, numerous vehicles have been picked over, and a large number have disappeared entirely, with Russia and the Ukraine both denying responsibility.