According to the Los Angeles Fire Department, a 30-year-old man in the tractor trailer was transported in serious condition to a hospital in Southern California.
The single-engine plane pilot died on the spot, firefighters said.
The plane took off from Torrance, about 20 miles to the north, with only the pilot on board, officials said. His destination was unclear.
Bystanders pulled the pilot out of the wreckage, and an emergency center gave them instructions on how to administer CPR until first responders arrived, firefighters said.
The National Transportation Safety Board said via Twitter that it was investigating the crash of the Piper PA-32 plane. The tweet said it was unclear whether an NTSB researcher will travel to the site.
The Federal Aviation Administration said it is also investigating the crash.
Media footage of the wreckage showed the engine and mutilated front fuselage, separated from the rest of the plane near a traffic stop.
Firefighters prevented a small amount of fuel on the ground near the plane from spreading.