MOSCOW — For a few terrifying seconds before a Polish jet crashed in western Russia on Saturday, its crew members knew they were about to die, Poland’s chief prosecutor said on Thursday, as investigators in both countries analyzed the contents of the plane’s black boxes.

“One could say that the crew was aware of the inevitability of the coming catastrophe, if only due to the plane shaking after the wings hit the trees, which we are certain happened,” the prosecutor, Andrzej Seremet, told a Polish radio station.

The plane crashed in thick fog on Saturday, killing Poland’s president, Lech Kaczynski, and 95 others, including many top civilian and military officials. Russian officials said the crew had been strongly warned about the poor conditions, leading to speculation that the pilot was pressed to land so the dignitaries would not be late for a ceremony commemorating the 70th anniversary of the Katyn massacre.

That theory was bolstered by an episode from 2008, when Mr. Kaczynski ordered a pilot to land in Tbilisi, Georgia’s capital. The pilot defied him, saying the conditions were too dangerous, and diverted to another airport.