Kaczynski and 95 others, including his wife, died in April 2010 when their Tu-154 plane crashed while trying to land in Smolensk, Russia, while there were no survivors.
Officials of the Interstate Aviation Committee, which investigates crashes in much of the former Soviet Union, said on Wednesday that the pilots were pressured to land by Poland`s air force commander, Gen. Andrzej Blasik, who was in the cockpit.
They said he had a blood-alcohol level of about 0.06 per cent, enough to impair reasoning.
Presenting the report IAC chairperson Tatiana Anodina said that the preparations for the president`s flight involved grievous mistakes.
"There were profound deficiencies in selecting and training the crew, assessing the readiness for the flight and determining alternative airports," states the report.
Further, when Lech Kaczynski`s plane took off from Warsaw, the crew did not have the actual weather forecast.
The IAC committee defines the major reason for the crash as "the crew not taking a timely decision to divert the plane to an alternative airport, in spite of receiving punctually and repeatedly the information about weather conditions at Smolensk-Severny Airport; the minimal weather requirements for this airport being set much lower."
Other important reasons include "descending to an altitude profoundly lower than the norm with the ground cues being out of sight" and "the crew not reacting in due manner to the repeated signals of the alarm system and early warning system."
"These reasons led to the plane striking obstacles and the ground in a human-directed flight, the demolition of the plane, and the death of the crew and passengers," Tatiana Anodina was quoted as saying by Russia Today TV.
A strong contributory factor to the crash was the presence of the Polish Air Chief in the cockpit, which had a "psychological impact" on the crew, the report said.
"The presence in the cockpit of the Polish Air Chief [Gen. Andrzej Blasik] and the [Foreign Ministry`s] chief protocol officer, and the expected negative reaction of the main passenger had a psychological impact on the crewmembers and influenced their decision to land in any conditions," Anodina said.
"The engines were operating until the impact with the ground," she underscored ruling out any terror suspicion.
It has also been confirmed that the airfield in Smolensk, Smolensk-Severny, and its equipment were suitable for accepting flights of all types of aircraft, including the Yakovlev-40 and Tupolev-154.