The aircraft was flying with another jet when contact with the plane was lost, said Coast Guard spokesman Henry Dunphy Wednesday night. Crews were searching for the F/A-18 Hornet in the area about 60 miles southwest of San Diego and 35 miles west of Ensenada, Mexico.
The Coast Guard was notified about the missing jet around 10:30 p.m. Wednesday, Dunphy said.
Several aircraft were being used in the mission. Two Coast Guard cutters and a Navy ship have been diverted into the area.
A spokesman for the Marine Corps confirmed the jet is assigned to the Marines.
The aircraft is based at Marine Corps Air Station Miramar in California, said Marine Corp. Capt. Brian Block.
Officials have not released how many crew members were aboard the plane. Additional details were not immediately available.