WARSAW, Poland -- Russian air traffic controllers gave incorrect and confusing landing instructions to pilots of a plane that crashed, killing Poland's president and 95 other people, a Polish report said Friday -- a finding that could further strain ties between the countries.
But the report into the crash proportions most blame on Polish officials and procedures. Poland's Defense Minister Bogdan Klich, whose ministry oversaw the training of the crew of the 2010 flight, resigned Friday.
The ">report challenges a Russian aviation commission report published in January that put sole blame for the disaster on Polish officials -- striking Poles as an attempt to avoid any responsibility for the crash in heavy fog at a rudimentary airport near Smolensk, 220 miles southwest of Moscow.
Since then, Poles have eagerly awaited their own experts' report, hoping it would create a more balanced picture. The accident on April 10, 2010, killed dozens of senior officials along with the president and first lady -- the worst Polish disaster since World War II.
As key causes of the crash it cites incorrect positioning of the Tupolev-154 during an attempted landing due to insufficient training of the pilots. It also cites a lack of proper cooperation among the crew and an overly slow reaction to an automatic terrain warning system that warned pilots they were flying too low.
Incorrect information from the airport's control tower on the plane's position also prevented the crew from realizing they were making mistakes, it said.
"There was no single cause, but an accumulation of causes led to the crash," said Jerzy Miller, the interior minister and the head of the investigation commission, during a presentation that lasted three hours.
In Moscow, the deputy chairman of the Russian Duma's foreign affairs committee, Andrei Klimov, said fault lies with the Polish pilots and lashed out at Warsaw for politicizing the investigation.
"This report is not a technical, but a political one," Klimov said. "The results were compiled with a nod to the political situation in order to show that Russians were to blame for at least something."
Alexei Morozov, the deputy head of Russia's Interstate Aviation Committee, said some of the report's conclusions were unclear.
He cited the report's "certainty that the aircraft commander had no intention to land, or that the presence of outsiders inside the cockpit, especially the Air Force commander of the Polish Republic, did not affect the decision of the aircraft commander."
He added that the committee would respond in more detail once it reads the entire report.
Polish Prime Minister Donald Tusk said Klich submitted his resignation Thursday evening, knowing that the report would point to mistakes in the military training of pilots and flight procedures.
The report did not point to any individual wrongdoing by Klich but painted a picture of overall negligence and an overly relaxed approach to security procedures. Klich said he was stepping down so as not to burden the government.
General elections are scheduled for this fall and Tusk's centrist party, Civic Platform, hopes to hold onto power.
Tusk immediately announced a replacement for Klich -- Deputy Interior Minister Tomasz Siemoniak -- and said the new minister would be charged with overhauling security procedures for government flights.
The report says main pilot, Capt. Arkadiusz Protasiuk, 36, did not have sufficient experience in flying a Tu-154 or in landing under difficult conditions. The only crew member who spoke Russian and could communicate with the airport, Protasiuk, was overwhelmed by many tasks and difficult conditions in the final moments, the report said.
It insisted Russian air traffic controllers played a role in the tragedy. Polish investigators found that the Polish plane was flying about 200 feet lower than the crew believed in the moments before it clipped a tree and crashed. The Polish commission said Russian air traffic controllers confirmed the plane was on the right course for descent, information that made the crew continue in the false belief they were making a proper approach.
The Polish report, which is available on the Internet in Polish, Russian and English, said the Russian air strip had insufficient lighting, contributing to a lack of visibility that morning. It had been out of service for months, but was reactivated for the needs of some flights -- also from Poland -- in April 2010.
The Russian and Polish reports also differ on a hugely sensitive issue: whether the crew faced pressure from the Polish head of the air force, and possibly even the president himself, to make a risky landing in heavy fog to stay on schedule.
Russian investigators said in January that the head of the air force, Gen. Andrzej Blasik, entered the cockpit -- with alcohol in his blood -- and pressured the pilots to risk a dangerous landing.
The Polish report confirms Blasik's presence in the cockpit, but says it did not play a role in the crash. It said investigators did not find any pressure on the crew and that pilots were not actually making a landing when the plane clipped a tree and crashed, just hundreds of meters from the runway. They had attempted an approach but were just starting to abort it, unable to see the ground and amid commands from a warning system to pull up.
"The crew were making the right decisions, but they did not know how to carry them out properly" due to insufficient training, Miller said.
The widow of Deputy Culture Minister Tomasz Merta, who was killed in the crash, said she considered the report incomplete because it was based on insufficient evidence. She noted that a key piece of evidence, the wreckage of the plane, remains in Russia and is not easily available to Polish investigators. Military prosecutors are conducting a separate investigation that is to single out and possibly charge those responsible for the crash.
The plane crashed as President Lech Kaczynski and his delegation were on their way to honor 22,000 Polish officers killed during World War II by Soviet dictator Josef Stalin's secret police, a crime known as the Katyn massacres.
The symbolism of the plane disaster occurring on a mission to remember the dead added another layer of Polish national grief and resentment in the weeks and months after the crash.
At first it seemed the accident had helped Poland and Russia heal some of their historic wounds. Russian President Dmitry Medvedev attended the Kaczynskis' funeral and there was a general outpouring of sympathy in Russia -- gestures greeted with Polish gratitude.
But the Russian report again strained relations, adding to a lingering sense of aggrievement in Poland. Poles remain bitter about the Katyn killings, the Soviet Union's occupation of Poland's eastern half during the war and Moscow's domination of Poland during the Cold War.
Right-wing Polish groups have promoted conspiracy theories, with some saying they believe Russians intentionally brought down the plane by producing artificial fog that blinded the pilots.
Miller said there was no artificial fog at the Smolensk airport that day.