WARSAW – The body of Poland's first lady Maria Kaczynska arrived home from Russia Tuesday to lie in state beside her husband, as thousands of mourners paid their respects to the tragic presidential couple.

Grieving Warsaw residents threw flowers at her cortege as it moved from the airport to the presidential palace, where her remains were reunited with those of President Lech Kaczynski following their deaths in a weekend air crash.

Draped with red and white Polish flags, their closed coffins were placed side by side as the couple's daughter Marta, 30, bowed at the foot of each one. Dignitaries and members of the public then began filing past.

Russian investigators have suggested that human error was to blame for Saturday's crash near the western Russian city of Smolensk that killed 96 people including dozens of senior Polish figures.

Both Polish houses of parliament held an emotionally charged special joint session on Tuesday to commemorate the crash, which happened as the plane headed to a memorial for Poles massacred by the Soviets in World War II.

"The tragedy has made a huge impression on all of us. We want to honour Mrs. Kaczynska, she was in the shadow of her husband but she seemed to be a very warm, a very decent woman," said Agnieszka 34, a public service worker.

Poland is holding a week of mourning for the dead.

The presidential couple will be buried on Sunday in Wawel castle in the southern city of Krakow, Poland's PAP news agency said, quoting officials.

An official memorial service for all the victims was due in Warsaw a day earlier.

A guard of honour stood to attention at the airport as the body of Kaczynska, 66, arrived from Moscow early Tuesday and a band played Poland's national anthem.

A ray of sunshine broke through leaden skies as her daughter placed her hands on the casket. The president's identical twin, conservative former prime minister Jaroslaw Kaczynski, 60, also knelt before the coffin.

In scenes that echoed the president's homecoming on Sunday, residents lined the streets along the 12-kilometre (eight-mile) route into the city, even though Tuesday was a work day.

Theories over the cause of the crash have swirled.

Russian air traffic controllers who handled the plane said Tuesday that the crew of the official jet, an ageing Tupolev Tu-154, refused three times to heed advice to divert to another airport.

One said the conversations between the crew and air traffic control had been in Russian, a language of which the Polish crew had a poor command.

Russian investigators have also ruled out a fire or explosion as the cause of the plane crash, Russian Deputy Prime Minister Sergei Ivanov said.

Polish prosecutors said there was no evidence the crew had been pressured by those onboard to override the advice so as not to miss the 70th anniversary memorial ceremony for the massacre at Katyn near Smolensk.

The accident, and Russia's swift and grief-stricken reaction, appears to have brought the historic foes together, with Prime Minister Vladimir Putin taking charge of the crash probe.

Almost half of the bodies -- 45 of the dead -- have been formally identified in Russia by relatives flown in to try to speed up the process, Russian Health Minister Tatyana Golikova said. Related article: Half of Polish air crash dead identified, says Russia

A conservative nationalist, Kaczynski was politically divisive both at home and abroad but his death has brought unity to Poland and political figures have been looking towards the future. Related article: Neighbours recall Kaczynskis as modest and friendly

Acting president Bronislaw Komorowski, the former parliamentary speaker appointed after the accident, said he could set a date for new presidential elections by Wednesday.

The vote must be held before the end of June. A presidential ballot was due later this year in any case, with Komorowski, a liberal, expected to run against Kaczynski.

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