This is strongly politicized in Poland, there have been many commissions and expertises, and despite most Poles thinking all the worst about Russia - majority (me included) does not believe it to be on purpose.
"Amid the endless political struggle, it is easy to lose perspective on the Smolensk Air Disaster as, first and foremost, a plane crash. Had the President not been on board to politicize the tragedy, it would have been obvious to everyone that the flight that day was a disaster waiting to happen. A poorly trained and unqualified crew was charged with flying VIPs into an ill-equipped, decrepit airport amid extremely dense fog."
“The plane was staying overnight in a hotel, as is often the case for large passenger aircraft relaxing between shifts,” the Kremlin spokesperson said.
“Unfortunately it had a few drinks, the window was open, and it fell out. Our thoughts are with the victims”.