The body of Polish President Lech Kaczynski will lie in state from today for grieving Poles to pay their respect.
The remains of his wife, Maria, have been flown back to Poland so their coffins can rest beside each other for the public memorial at the presidential palace in Warsaw.
The couple died along with 94 others in a plane crash in western Russia on Saturday.
Russian officials have said the pilots had ignored weather warnings and repeatedly tried to land at the fog-bound Smolensk airport.
Polish prosecutors said there was no evidence the crew had been pressured by those onboard to override the advice, so as not to miss a ceremony for Poles massacred after their capture by Soviet forces in World War II.
Besides the Kaczynskis, the plane was carrying military leaders, members of the political elite, the central bank governor and relatives of victims of the 1940 Katyn massacre.
The crash happened almost exactly 70 years after the original Katyn tragedy and near the notorious forest where Joseph Stalin's secret police shot dead 20,000 Polish officers.
Relatives of the crash victims have been flown to Russia to try to speed up the process of identifying the corpses.
Poland, in the midst of seven days of mourning, is to hold an official memorial service on Saturday for Mr Kaczynski and the other victims. He will be buried on Sunday.
Russian Prime Minister Vladimir Putin has taken charge of the crash inquiry and promised an 'objective and thorough' investigation.
Russia observed a day of mourning for the victims yesterday, flying flags at half mast and banning all advertising on television and radio.
The European Union also held a day of mourning yesterday, while NATO's political governing body held a minute of silence at its Brussels headquarters.
Parliamentary speaker Bronislaw Komorowski is assuming the duties of acting head of state.
He said he will set the date of a presidential election tomorrow and the vote must take place before the end of June.
In Ireland, books of condolence have been opened for all those who died in the crash.
In Limerick they will be available for signing at the City Hall and at Limerick County Hall in Dooradoyle.
Mayor of Limerick Cllr Kevin Kiely said he wanted to express his sympathy to the very large Polish community living in Limerick city and throughout the mid-west, where an estimated 6,500 Polish nationals live.
Pat O’Sullivan, Chairperson of the Limerick Polish Society, said this was the worst national tragedy to hit the Polish people since WWII.
He appealed to people in the city to sign the book to show solidarity with the polish community.
In Dublin, a book of condolence remains available for signing at the Polish Embassy in Ballsbridge until tomorrow night.
A book has also been opened at City Hall in Galway and is available to be signed between 9am and 4pm daily.
Books of condolences will also open at Belfast City Hall and in the Guildhall in Derry.