Thousands of people are gathering in Krakow for the state funeral of Polish President Lech Kaczynski.
After a funeral Mass, the president will be buried in Wawel Cathedral, the resting place of Poland's kings and national heroes.
He and 95 others died eight days ago when their plane crashed in fog en route to a ceremony in Russia.
Many world leaders cannot attend because flights have been grounded by Iceland's volcano.
Russian President Dimitri Medvedev flew to Krakow, despite air travel restrictions.
The state funeral will begin with a Mass at Krakow's St Mary's Basilica.
From the city's mediaeval market square, the coffins of the first couple will be carried along a route lined with Polish flags with black ribbons and photos of Lech Kaczynski and his wife Maria.
Their final resting place will be the royal crypt in the historic Wawel cathedral, alongside the nation's kings and heroes.
The decision to entomb a leader seen as divisive by many during his lifetime in such a hallowed place has sparked protests.
Huge crowds are expected to attend the funeral after a week of national mourning.
The Polish government airliner crashed in western Russia on 10 April. Investigators believe pilot error caused the plane to hit tree-tops in heavy fog in the Smolensk region, where the Polish delegation had meant to attend a memorial for Poles massacred by Stalin's secret police at Katyn in World War II.
Key Polish political and military leaders were killed in the crash, including the heads of all three branches of Poland's military.
On Saturday, hundreds of thousands of people took part in an open-air memorial service in the centre of Warsaw.
US President Barack Obama will not attend Mr Kaczynski's state funeral on Sunday because of the travel chaos across Europe, the White House said.
Other figures unable to attend include the UK's Prince of Wales, French President Nicolas Sarkozy and German Chancellor Angela Merkel.
A number of eastern European leaders have said they will attend by driving to Krakow.
All airports in Poland remained closed on Saturday, including Balice in Krakow where most of the dignitaries were to arrive on Sunday.
