At least seven people were also injured in the crash on Monday evening, Health Minister Adam Niedzielski said.
People had been sheltering from bad weather in the hangar, Polish media reported, quoting the fire brigade.
Fire brigade spokeswoman Monika Nowakowska-Brynda said the weather was a "probable cause" for the crash.
Four helicopters and 10 ambulances were dispatched to the scene of the incident in the village of Chrcynno, 47 kilometres (29 miles) from Warsaw.
Polish media identified the plane that crashed as a Cessna 208.
