Debris is seen at the crash site of the Caspian Airlines plane, which fell into farmland near the city of Qazvin, northwest of Tehran on July 15, 2009. The Iranian airliner en route to neighboring Armenia crashed, killing all 168 people on board in the worst air disaster in Iran in recent years. (Xinhua/Liang Youchang)

The plane carrying Polish President Lech Kaczynski crashed near the Smolensk airport on April 10 of 2010, killing the president and all 132 people on board, said Russian officials. (Xinhua/Lu Jinbo)

Rescuers work at the crash site of a passenger plane near the city of Uroumieh in northwest of Iran on Jan. 9, 2011. A passenger plane with over 100 passengers on board crashed in northwest Iran, with at least 35 passengers surviving and scores killed, the local English language satellite Press TV quoted an unnamed red crescent official as saying. (Xinhua/Mehr, Esfandiar Asgharkhani)

An airliner crashed in the Democratic Republic of the Congo (DRC) on July 8 of 2011 as it tried to land in bad weather, killing 127 people. (Xinhua/AFP Photo)

Military personnel move the body of the four victims in an air accident near Juan Hernandez Islands in Santiago, capital of Chile, Sept. 3, 2011. An aircraft with 21 passengers onboard including a television team crashed near the Juan Hernandez islands, about 700 kilometers off the continent. (Xinhua/Victor Rojas)

Rescuers and investigators work at the site of plane crash near Russia's Siberian city of Tyumen, on April 2, 2012. At least 31 people were killed when a passenger plane crashed in Russia's Siberia region early Monday, emergency authorities said. (Xinhua/Li Yong)

A Pakistani soldier searches the plane crash site on the outskirts of Islamabad, capital of Pakistan, on April 21, 2012. All passengers and the crew aboard a Pakistani plane that crashed near Islamabad have been declared dead after the rescue teams found the wreckage, the country's Interior Minister Rehman Malik said.(Xinhua/Ahmad Kamal)

A relative of missing passengers crys in Halim Perdana Kusuma airport, Jakarta, Indonesia, May 9, 2012. Search and rescue was underway after a Russian-made commercial plane with at least 46 people on board went missing in West Java, Indonesia, spokesman of Transport Ministry Bambang Ervan said. (Xinhua/Agung Kuncahya B.)

The wreckage of the crashed plane is seen near the Lagos airport in Nigeria, June 3, 2012. A passenger plane carrying 153 people crashed into a two-storey building in Nigeria's southwestern Lagos State on Sunday, killing all the people on board and 40 others on the ground. At least four Chinese were among the passengers, the Chinese Embassy in the West African country has confirmed. (Xinhua File Photo)

The black box of the crashed Sita Air plane is taken for investigation in Kathmandu, Nepal, Sept. 28, 2012. Nineteen people including three crew members were killed after the Dornier Aircraft 9N-AHA of Sita Air crashed just a kilometer far from the Tribhuvan International Airport (TIA) in Kathmandu. (Xinhua/Sunil Sharma)

A plane operated by Lion Air with over 100 passengers on board crashed into sea while landing at an airport in Bali on April 13, 2013. (Xinhua File Photo)