The crew of Mr Kaczynski's plane, who were all members of the Polish Air Force, were said by investigators to have ignored repeated warnings not to land in thick fog. They are now studying black box recordings to try to work out why the pilot did not divert to another airport.
Speaking at a meeting with the Prime Minister, Vladimir Putin, who is in charge of the investigation, Russia's chief investigator Alexander Bastrykin, said: "The recordings that we have confirm that there were no technical problems with the plane.
"The pilot was informed about complex weather conditions but nevertheless made a decision to land."
Teams continued to sift through the wreckage of the plane at Smolensk, where Mr Kaczynski and those on board, including Poland's army chief, the navy chief commander, and the governor of the Polish central bank, were heading to honour 22,000 Polish officers killed at Katyn by the Soviet secret police in 1940.
The news came as a shocked and grieving Poland welcomed home the body of its president. Hundreds of thousands lined the streets of Warsaw to pay their respects as Mr Kaczynski's cavalcade wound its way through the capital to the presidential palace.
Investigators in Russia, who have been joined by Polish teams, have said that Captain Arkadiusz Protasiuk, 36, the flight's first officer, had made three abortive attempts to land, and had been advised to fly to another airport, before deciding to make one last attempt. Both Captain Protasiuk and his second officer, Major Robert Grzywna, were experienced pilots with more than 5,000 hours of flying experience between them.
Lech Walesa, the Solidary founder and former president, said: "Someone must have been taking decisions on that plane. I don't believe that the pilot took decisions single-handedly," he told reporters. "That's not possible. I have flown a lot and whenever there were doubts, they always came to the leaders and asked for a decision, and based on that, pilots took decisions. Sometimes the decision was against the leader's instructions."
However, questions were being asked last night about why a roll-call of Poland's influential politicians and military chiefs were allowed to travel on the same Tu-154 aeroplane. Russian has withdrawn its Tu-154 fleet, the workhorse of Eastern Bloc civil aviation in the 1970s and 80s, from service because the planes are expensive on fuel and do not meet international noise restrictions. While there have been 66 crashes involving the planes in the last four decades, Poland has not retired the aeroplane because of cost. The presidential plane was fully overhauled in December.
Gregorz Holdanowicz, a Polish military aviation expert, said the only rule as that the president, the prime minister and the speaker could not travel on the same plane. He said that the cost of flying so many out to the event would have been a reason for carrying so many dignitaries on the same flight.
While Polish-Russian relations had been improving recently, there had been enmity between the two dating back to the Katyn slayings. President Kaczynski had angered the Kremlin with his as a staunch defender of Ukraine and Georgia against what he called Russia's "new imperialism". He had also supported the decision to allow the US to use Poland as a base for its missile shield programme.
There have been mounting conspiracy theories about Russian involvement in the crash appearing on the internet. Fyodor Lukyanov, a political analyst and editor of the journal Russia in World Affairs, said: "Kaczynski was, to put it lightly, not a friend of Russia. Nonetheless, he is being treated with the utmost respect by the Russian leadership.
"This crash, however, is symbolically very gloomy ... and may reinforce in Poland the notion that everything associated with Russia is awful and bad.
"Even if it is confirmed that pilot error caused the crash, there will inevitably be those who say it was the KGB that killed Kaczynski."
However, Witold Waszczykowski, deputy head of Poland's National Security Bureau, said: "We did not expect this gentle, kind approach, this personal involvement from Putin,
"Naturally it will have a positive impact on the relationship between our countries. I can imagine a high-ranking Russian delegation from Moscow coming to Kaczynski's funeral."
In Poland, people were still struggling to come to terms with an accident described by Donald Tusk, the nation's prime minister, as the worst tragedy to befall the nation since the end of the Second World War.
At midday on Sunday air-raid sirens wailed in Warsaw and across the country church bells tolled as Poles observed two minutes of silence as a precursor to a week of official mourning.
Jaroslaw Kaczynski, the president's twin brother who travelled to Russia to formally identify the body, is said to be "devastated" by his loss. In a grim and sad ceremony the surviving Kaczynski knelt and prayed at the crash site for a man whose whole life and political career had been so much entwined with his own.
Bronislaw Komorowski, Poland's acting president, now has 14 days to call new presidential elections, which must then take place within 60 days.
Who from President Kaczynski's Law and Justice party will run for office is not clear, with the crash claiming the lives of other leading party lights, only Jaroslaw might have the necessary stature needed for a bid for the presidency.
The crash also delivered a devastating blow to the Polish army, which lost a number of its senior commanders at a time of intensive activity for the country's armed forces. Poland has over 2,000 troops engaged in combat in Afghanistan and the loss of so many generals could not have come at a worse time.
The date of Mr Kaczynski's funeral has not yet been set.
