The single-engine Piper PA-32 had mechanical problems after taking off from Montgomery-Gibbs Executive Airport on Tuesday.
It was trying to land in a nearby field but instead went down in the southbound lanes of Interstate 5, north of California’s second-biggest city shortly after noon, authorities said.
It clipped several cars and came to rest partially on the central divider.
Two people in the cars were taken to a hospital for treatment of minor injuries, including slight cuts from broken glass, according to the California Highway Patrol. The two people aboard the plane appeared to be unhurt.
Dane and Sarah Tribett of Austin, Texas, were in town to celebrate their eighth wedding anniversary when their Kia sedan was hit by the plane, although they escaped serious injuries.
"Glass shattered everywhere. All of a sudden we just see the plane in front of us," Sarah Tribett told KSWB-TV. "We were scared out of our minds."
"The people that were driving behind us drove by us after and let us know that it literally landed on top of our car," she said. "There's jet fuel all over the back of our back seat. All of my clothes are soaked and there's just glass everywhere."
Part of the plane's right wing broke off and became lodged in the back of an Audi SUV.
The freeway was shut down for more than four hours until a small fuel spill was cleaned up and the plane was hauled away.
