The US Transportation Security Administration is looking into how a man newly paroled from jail breached airport security and boarded a commuter flight at San Diego Airport before he was arrested, authorities said.
The would-be stowaway, Marc Rory Duncan, 38, was removed from a United Express plane at the gate just before it was scheduled to depart on a flight to Los Angeles on Tuesday and was taken into custody, police said.
San Diego Harbour Police Lieutenant James Jordan told reporters Duncan had been released from jail the night before. He had been serving time for theft, according to CNN.
The TSA said in a statement confirming the incident and subsequent investigation that "as is the case with any incident of non-compliance with security protocol, TSA has initiated an investigation and if necessary, will take appropriate action."
Duncan entered the commuter terminal at Lindbergh Field around 11 am on Tuesday, walked through an unlocked emergency exit onto the tarmac and onto the plane with 27 passengers onboard bound for Los Angeles, about 130 miles away, Jordan said.
The opened emergency door set off an alarm, but by the time security personnel and police responded, Duncan had blended in with the passengers boarding the plane, he said. But the flight crew noticed something was amiss.
"The pilot was doing his safety walk and checked with the flight attendant. He was supposed to have 27 passengers, and the flight attendant count was 28," Jordan said. "Mr Duncan got up on his own and gave up; he walked himself off the plane."
Police arrested Duncan, who was not armed and had not bought a ticket, he said.
"He was making some pretty incoherent statements," Jordan said.
The TSA and police then inspected the plane, delaying take-off for about two hours.
"All the passengers had to be rescreened," he said, adding that the plane was also searched by a canine team for explosives. None was found.
Duncan was being held on suspicion of violating his parole and two misdemeanour offences for breaching security. He will be arraigned on Thursday.
"He got out of jail on Monday and he was back in jail Tuesday," Jordan said.