Warsaw , Poland ( CNN ) -- Polish legislators were planning Wednesday to hold a June election to choose a successor to President Lech Kaczynski , whose death in an air crash is generating unprecedented scenes of public grief . Mourners lined up through the night outside Warsaw 's Presidential Palace to pay respects to Kaczynski , whose body is lying in state alongside that of his wife . However , amid national unity in the wake of the disaster , there were the first signs of discord with protests reported over a decision to bury the late president and his wife in a crypt previously reserved for monarchs and saints . The couple were among 96 Polish dignitaries , military top brass and officials who died when the plane carrying them to a service commemorating Polish prisoners of war massacred in Russia during World War II crashed in bad weather . Their bodies were repatriated earlier this week . Caskets carrying 30 more crash victims were returned to Poland on Wednesday aboard a military jet from Moscow . Draped in Polish flags the caskets were lined up side-by-side by an honor guard during a solemn ceremony at Warsaw 's airport . iReport : Share your photos , video and stories with CNN . The disaster has caused shockwaves through Poland , with thousands of people waiting up to eight hours to pay their respects to the first couple . Due to overwhelming demand , the palace was opened to the public through the night . A line of up to 15,000 mourners , many dressed in black and carrying pictures of the deceased first couple , could be seen snaking through the center of Warsaw Wednesday . Images of Poland 's collective grief . `` I think this is really unique to Poland , '' U.S. ambassador to Poland , Lee Feinstein told CNN , adding that the devastation to the country 's leadership was unparalleled in the contemporary world . Feinstein described Poland as one of the United States ' `` staunchest '' allies , largely thanks to military support for U.S.-led operations in Iraq and Afghanistan . U.S. President Barack Obama is expected to be among international figures attending the first couple 's funeral service in Warsaw , scheduled for Saturday . The Kremlin in Moscow said Russian President Dmitry Medvedev would also attend . The service will be followed by the couple 's burial on Sunday in Krakow 's Wawel Castle . The archbishop of Krakow said burying the late president in the historic crypt was the country 's way of honoring him . `` I think in this way the Polish nation wants to include him among the greatest and most revered men in Polish history , '' Stanislaw Dziwisz said on Polish state television . There have been reports of protests in Krakow over the decision , while debate has raged online as to whether Kaczynski , seen as unpopular prior to his death , should be buried in a national heroes ' cemetery in Warsaw rather than at Wawel . Biography : Lech Kaczynski . A Facebook group opposed to the castle burial had garnered 32,000 followers by late Wednesday . According to Poland 's PAP news agency , a date for the election that will choose Kaczynski 's successor will be announced on April 21 by acting President Bronislaw Komorowski . The agency said the date was likely to be June 13 or 20 . Under Poland 's constitution Komorowski must call the election within 14 days of the president 's death with the vote taking place within 60 days . CNN 's Antonia Mortensen in Warsaw , Poland and Maxim Tkachenko in Moscow , Russia contributed to this story .
Iraq set to hold Wednesday election to replace president killed in air crash . Mourners line up for up to eight hours to pay respects to first couple . Controversy breaks out over decision to bury Feinstein alongside former monarchs .