An image from 2015 shows a Pakistan International Airlines plane preparing to leave Chitral for Islamabad. A different plane flying that same route crashed Wednesday. Farooq Naeem/AFP/Getty Images hide caption

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Farooq Naeem/AFP/Getty Images

A woman mourns at a makeshift memorial for the victims of a jetliner crash outside Pulkovo International Airport in St. Petersburg on Tuesday. Vasily Maximov /AFP/Getty Images hide caption

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Vasily Maximov /AFP/Getty Images

A family leaves flowers and toys at an entrance of Pulkovo airport outside St. Petersburg, Russia, during a day of national mourning for the plane crash victims. Dmitry Lovetsky/AP hide caption

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Dmitry Lovetsky/AP

Emergency services attend the scene on the A27, where seven people died after a plane crashed into cars on the major road during an aerial display at the Shoreham Airshow in West Sussex. Daniel Leal-Olivas/PA Photos/Landov hide caption

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Daniel Leal-Olivas/PA Photos/Landov

Officials work on the scene of a vintage airplane that had been piloted by actor Harrison Ford when it crash-landed in March on the Penmar Golf Course in the Venice area of Los Angeles. Federal safety investigators have concluded that a problem with a carburetor part led to engine failure. Damian Dovarganes/AP hide caption

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Damian Dovarganes/AP

An image from AFP TV video taken Tuesday shows smoke billowing from scattered debris of the Germanwings Airbus A320 at the crash site in the French Alps above the town of Seyne-les-Alpes, France. Denis Bois/AFP/Getty Images hide caption

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Denis Bois/AFP/Getty Images