Buenos Aires, Argentina ? An unruly passenger on a United Airlines flight from Miami to Buenos Aires tried to force his way into the cockpit Thursday, managing to smash in part of the reinforced door before a co-pilot clubbed him with an ax.

Other crew and several passengers then began wrestling with Pablo Moreira, 28, subduing him after a chaotic, 10-minute struggle.

Moreira, a banker from Uruguay, was restrained for the remainder of the flight, the airline and the FBI said. A flight attendant received minor injuries in the struggle.

Moreira, who was lucid and in stable condition, was whisked into custody when the jetliner landed safely in the Argentine capital of Buenos Aires as scheduled at 10:30 a.m. local time, said Judy Orihuela, an FBI spokeswoman in Miami. He was provided medical treatment.

It was not clear what prompted the man to try to enter the cockpit. Orihuela said he was not armed and did not appear drunk. Gordon Johndroe, a spokesman for President Bush’s Homeland Security Council, said there was nothing to indicate the incident was an act of terrorism.

But the incident raised new questions about access to airplane cockpits in the wake of the Sept. 11 terrorist attacks.

United Airlines has reinforced its cockpit doors with metal bars, and Chairman and CEO Jack Creighton credited the measure with helping to stop Moreira. “The passenger never gained full entry,” he said in a statement.

Moreira kicked in a small breakaway panel across the bottom half of the door and managed to get his head inside the cockpit before the co-pilot hit him, United spokeswoman Chris Nardella said. Cockpits are equipped with small axes for emergencies.

Moreira began kicking the cockpit door about five hours after the midnight flight left Miami, carrying 157 people, authorities said. He was shouting that he wanted to talk to the pilot as he rushed to the front of the plane, passengers said.

United said flights to and from Argentina would continue as scheduled.