The incident happened around 11 p.m. Thursday on West 27th Street, just below the 210 Freeway in San Bernardino.
Authorities aren't sure why the red 1999 Mitsubishi Eclipse drove off the freeway and landed on a surface street. The car sustained extensive damage.
One witness said she was nearly hit by the flying car.
"It was scary because they almost hit my car. They almost landed on top of my car," said Maria Bryant. "I had my 6-year-old daughter in the car with me."
Bryant said she stopped another car to help the victims. Two adults and two children were taken to the hospital. Their conditions are not known.
