A report has found that faulty equipment and poor communication by Russian ground staff contributed to the plane crash that killed Poland's president.
The Polish government commissioned the report into last year's crash in Smolensk that killed President Lech Kaczynski and 95 others.
The 15-member expert commission also said many of the Polish air crew lacked appropriate training for the flight and some equipment on board their TU-154 Tupolev was not properly prepared.
President Kaczynski, his wife Maria, many senior officials and top military personnel died as their plane was trying to land in thick fog on 10 April 2010.
'The commission has established that the lighting systems at the (Smolensk) airport were faulty and inadequate,' commission member Lieutenant Colonel Robert Benedict told a news conference.
The Russian side gave wrong orders to the plane's pilots, who Col Benedict said were making only a trial descent rather than seriously attempting to land when the crash happened after miscalculating their distance from the ground.
The Polish delegation had been heading to the nearby Katyn forest to commemorate the 70th anniversary of the murder of Polish officers by Soviet secret police during World War Two.
The commission had some sharp criticism for the Polish side, saying that the pilot lacked experience in landing aircraft in adverse weather conditions.
He was also the only Russian-speaking crew member, which meant he had to deal directly with the ground staff in addition to flying the plane.
Equipment on board the plane had not been properly prepared, another member of the commission, Wieslaw Jedynak, told the news conference.
However, the report said there was no evidence that Mr Kaczynski or other passengers had put pressure on the pilots to land against their wishes.
Some media and politicians have suggested the pilots had tried to land the plane under duress.
In its own report into the disaster, published in January, Russia put all the blame for the disaster on the Polish crew.
That report angered the Polish side, which said conditions at Smolensk airport had also been a contributing factor.
Mr Kaczynski's identical twin brother Jaroslaw, who heads Poland's main opposition party, has accused Prime Minister Donald Tusk's government of conniving with Russia to cover up the full truth of the Smolensk disaster.
Mr Tusk, who is tipped to win re-election in October, strongly denies the claims.
