Poland has released transcripts of cockpit conversations from the plane which crashed in Russia in April, killing the country's president and 95 other people on board.
The transcripts reveal that the pilots received at least a dozen warnings from on-board systems to regain altitude during the last minutes before the crash.
"Pull up, pull up... Terrain ahead," the warning system told the pilots numerous times just before the crash.
The interior ministry published the transcripts on its website on Tuesday to quell media speculation about the reasons for the accident.
All passengers and crew were killed in the April 10 crash, including Lech Kaczynski, the president, his wife, senior military commanders and many parliamentarians.
It was not clear from the transcripts why the pilots did not try to pull higher until it was already too late.
One of the pilots cursed after the plane hit a tree - a collision that flipped the Tuploev Tu-154 military plane upside down.
The last sound recorded was a prolonged curse by an unidentified person in the cockpit.
Polish media have speculated that Kaczynski himself may have contributed to the crash by encouraging pilots to attempt to land the plane despite the poor weather conditions, disregarding Russian traffic controllers' advice.
The transcript provided no evidence of this, though three minutes before the crash it quoted an unidentified person in the cockpit as saying: "[S]he will be annoyed if..."
It did not make clear who the subject of the sentence was and said the rest of the sentence was unintelligible.
Kaczynski and his entourage had been running late for a ceremony in the city of Smolensk marking the 70th anniversary of the Katyn massacre in which more than 20,000 Polish army officers and intellectuals were killed by Russian forces.
About 15 minutes before the crash, the pilots told Mariusz Kazana, the head of Poland's diplomatic protocol who was in the cockpit, that the plane would not be able to land because of the thick fog, the transcripts showed.
"Well then we have a problem," Kazana replied.
A few minutes later, he returned to the cockpit to say the president had not yet made a decision about what they should do next.
Russia, which is conducting its own probe into the crash, handed over copies of the cockpit recordings to Poland on Monday.
A Polish prosecutor who took part in a Russian probe into the crash has said he believes poor training, lack of money for test flights and incorrect flight procedures in the Polish air force all contributed to the accident.