The cause of the plane crash that killed Polish president Lech Kaczynski has been attributed to the crew's refusal to divert to another airport under pressure to avoid upsetting the president.

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Special coverage on Polish plane crash

Interstate Aviation Committee (IAC) chairwoman Tatyana Anodina outlined in Moscow Wednesday the findings of the Russian investigators' final report into last April's crash near Smolensk, which killed all 96 people on board including Kaczynski and many of Poland's leaders.

The IAC head told a press conference the crew of the Tu-154 plane refused to head for an alternative airport due to an expected negative reaction from president Kaczynski.

The flight recorder, or black box, recorded no command from the president ordering the plane to land in Smolensk. However, it showed that crew members feared the president would be angry if they aborted the plan to land.

"He'll get mad," one of the plane's crew members was recorded saying by the black box.

Anodina also said the presence of top officials, including the Polish air force commander, in the cockpit put psychological pressure on the crew and influenced its decision to land in Smolensk.

The report said investigators had found alcohol in the blood of the Polish air force commander.

Meanwhile, Anodina cited the report as saying the crew showed failures in training.

"There were serious flaws regarding the preparation of the crew and control over the flight," she said.

In addition, the report confirmed there was no explosion or fire before the plane's clash.

"There was no fire, explosion, or destruction of the plane in midair before it hit obstacles," Anodina told the conference.

"The technical commission has found that the plane was in working condition before its departure from Warsaw. There was no failure of the plane, its engines or systems during the flight," she said.

The chairwoman said the IAC was ready to accept any international investigation of its report.

"Concerning international investigations or audits, the IAC's technical commission and experts would be ready to provide the relevant substantiation and explanations at any professional level," Anodina told the conference.

"We are strictly guided by the Chicago Convention and the air accident investigation rules," she said.

Anodina also stressed there was no pressure exerted on the IAC during its investigation.

"As a professional, I have not encountered any form of pressure while working for the IAC," she said.

Earlier on Wednesday, the IAC said on its website it had handed the final report to the authorized representative of Poland via the Polish embassy in Russia.

Local media reported the Polish side had passed back the report with its comments to the Russian state commission on Wednesday.

In December, Polish Prime Minister Donald Tusk rejected a draft of the final report, saying the probe was "unacceptable".

Russian authorities promised in October they would not publish the findings until Poland commented on it.

According to preliminary findings released earlier last year, the crew ignored warnings that heavy fog made conditions unsuitable for landing.