Zeqir Rexhaj, 49, told 20 Minuten newspaper he helped free the 70-year-old man from the burning aircraft wreckage after driving along a road where the accident occurred near the municipality of Muhen.
The pilot took off in the single-engine plane from Grenchen in the canton of Solothurn at around noon but after experiencing problems over K!olliken in the canton of Aaargau he tried to land it in a field, Aaargau cantonal police said in a statement.
The aircraft clipped the edge of a guardrail on a road before colliding with a car being driven toward Aarau, police said.
The plane caught fire as it landed in a field while the car flipped onto its roof.
Rexhaj, a Kosovar, said he has driving home from work when he saw the crash.
“I stopped immediately and ran to the scene of the accident,” he told 20 Minuten.
When he saw the woman in the car was not in mortal danger he decided to help the pilot, the newspaper said.
Rexhaj said two other men helped him pull the pilot out of the plane.
“I took a blanket from the car involved in the accident and we extinguished his burning legs . . . his eyebrows and his legs were burning.”
The pilot was flown to hospital for treatment of burns.
The driver of the wrecked car, a 30-year-old Swiss woman, was also admitted to hospital with serious injuries, Aargau cantonal police said.
The federal office for civil aviation has opened an investigation into the accident.
UPDATE: The 70-year-old pilot died from his injuries at the Zurich university hospital, police said on Monday.