SMOLENSK (AFP/Reuters) A Soviet-era jet carrying Polish President Lech Kaczynski and much of the military and state elite crashed in thick fog in Russia on Saturday killing all 97 people on board in a blazing inferno. The Tupolev Tu-154 was taking Kaczynski and his wife, the military chief of staff and other top officers, central bank governor, deputy foreign minister, members of parliament and other senior officials to a memorial ceremony for thousands of Polish troops massacred by Russian forces in World War II. The jet hit treetops in fog as it approached the runway at Smolensk airport in western Russia and broke up in flames, regional governor Sergei Antufiev said. It clipped the tops of the trees, crashed down and broke into pieces, Antufiev told Russia-24 television news network. Pilot error was a possible reason for the crash, said Andrei Yevseyenkov, spokesman for the Smolensk local government. A Russian air force official told news agencies that the crew repeatedly ignored instructions from air traffic controllers. Wreckage was scattered across a forest and parts of it burned for more than an hour. The two black box flight recorders were quickly found, news agencies reported. As well as killing the 60-year-old head of state, the crash devastated Polands military leadership. The 88 passengers included General Franciszek Gagor, chief of Polands armed forces and the heads of all the main armed forces, Central Bank Governor Slawomir Skrzypek, Deputy Foreign Minister Andrzej Kremer, Kaczynskis wife Maria, and scores of MPs, historians and other officials. The body of Kaczynski has been recovered at the crash site, Russian state news agency RIA Novosti reported. Identification of many of the dead will require additional expertise, including DNA analysis, the agency quoted the official as saying. Authorities have found one of the flight recorders of the plane carrying the Polish President, news agencies reported. One of the flight recorders has been found at the scene of the crash, the Interfax news agency quoted a regional government source as saying. This kind of dramatic tragedy is unheard of in the modern world, Polish Prime Minister Donald Tusk said after an emergency cabinet meeting. Former Polish president Lech Walesa, who headed the Solidarity movement, called the disaster inconceivable. The Soviets killed Polish elites in Katyn 70 years ago. Today, the Polish elite died there while getting ready to pay homage to the Poles killed there, a shaken Walesa told AFP. A party source said Kaczynski twin Jaroslaw Kaczynski was not on board the plane that crashed. Bronislaw Komorowski, head of Polands lower house, took over as interim head-of-state. He ordered a week of official mourning, declaring: We are united - there is no left or right - we are united in national mourning, The Polish cabinet held an emergency cabinet meeting as did the military leadership. The delegation was to attend a memorial service in the Katyn Forest, near the crash scene, for the 22,000 top Polish officers and troops killed by Soviet troops 70 years ago. The event had been intended to help reconciliation between Poland and Russia. The jets engines and a large chunk of its mud-caked tailfin were strewn over a large area in the fog-blanketed forest - which is only a few kilometres from Katyn. The jet had been fully repaired and refurbished in December, Alexei Gusev, director of the Aviakor aircraft factory that makes the planes said. Russian President Dmitry Medvedev appointed Prime Minister Vladimir Putin to head an inquiry commission and sent Emergency Situations Minister Sergei Shoigu to the site. Kaczynski and his twin brother formed a formidable dual leadership of Polands nationalist right wing, stubbornly taking on other European leaders at EU summits to defend his countrys cause. He faced an election later this year but was to fight for a new term. Putin called Tusk to express condolences over the tragic crash, the Russian leaders spokesman Dmitry Peskov told Russian news agencies reported. World leaders expressed shock at the disaster. US President Barack Obama hailed the late President as a distinguished statesman who played a key role in the Solidarity movement, and he was widely admired in the United States as a leader dedicated to advancing freedom and human dignity. French President Nicholas Sarkozy paid homage to his Polish counterpart as a man driven by ardent patriotism, who dedicated his life to his country. He will be mourned across the world and remembered as a passionate patriot and democrat, said British Prime Minister Gordon Brown.