The body of Poland's First Lady, Maria Kaczynska, has been flown to Warsaw to lie in state alongside that of her husband, President Lech Kaczynski.
Poland has seen an outpouring of grief since the couple and scores of other top Polish officials died in a plane crash in western Russia on Saturday.
Poland's parliament will hold a special session later to discuss the disaster.
Mr Kaczynski's body returned to Poland on Sunday. The bodies will begin lying in state on Tuesday or Wednesday and the funerals are expected to be held at the weekend, the BBC reports.
Ninety-six people died when the plane clipped tree-tops as it tried to land in thick fog at a former air base north of Smolensk city.
Russian officials say the pilots of the Soviet-built airliner had ignored weather warnings and repeatedly tried to land. Polish prosecutors have stressed there is no evidence that the crew were pressured by those onboard to ignore the advice.
Mr Kaczynski and his party of senior Polish military and political officials had been due to attend a memorial for the Polish victims of a World War II massacre by Soviet secret police at Katyn.
At least 130 family members have been flown to Moscow to help forensic scientists identify their bodies.