A small private aircraft violated the airspace in the no-fly zone as President Barack Obama was about to leave from Los Angeles International Airport aboard Air Force One, authorities said.
The North American Aerospace Defense Command scrambled two F-16 fighter jets to intercept the Piper 28 aircraft over northeast Los Angeles at approximately 9:45 a.m.
The jets followed the private plane until it landed about five minutes later and was met by local law enforcement, NORAD said in a statement.
The pilot of the unidentified plane was forced to land at El Monte Airport, detained for questioning and released after the incident considered a mistake, according to Lt. Dan Burlingham, of the El Monte Police Department.
No details were available about where the pilot was headed.
"It appears, as far as we know, that it was just a mistake,'' Burlingham told the Associated Press.
Obama departed from Los Angeles the morning after a fundraising visit where he raised $15 million -- a record for a single fundraiser -- at a dinner with some 150 Hollywood donors at the home of George Clooney.
A similar incident was reported Feb. 16, when a Cessna with 40 pounds of marijuana was intercepted and forced to land at Long Beach Airport.