This week a Polish radio station, RMF FM, leaked a transcript of cockpit recordings suggesting that presidential aides had put pressure on the pilots to land at Smolensk despite thick fog.
Polish military prosecutors called the transcript "imprecise".
The plane wreckage remains in Russia.
The disaster happened as the president, his wife and top government officials were travelling to Katyn, the remote wooded spot where Soviet secret police murdered thousands of Polish officers in 1940.
The Russian-built Tupolev Tu-154 airliner crashed just short of the runway near Smolensk in western Russia, after it hit trees in heavy fog.
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