A passenger tried to enter the cockpit of an international flight out of Miami Thursday — but was overwhelmed by the crew and passengers after the co-pilot hit him over the head with a fire ax. 

Even after the blow, it took the other crew members and several passengers no less than a chaotic, 10-minute struggle to subdue Pablo Moreira, 28.

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.

But David Stempler, president of the Air Travelers Association, a passenger group, said Thursday's incident showed further security steps are needed.

"There are vulnerabilities in the system put in place involving a single bar across the door," he said. "Maybe they could put in additional bars."

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.

"You could look up from the aisle and see the whole cabin crew had rushed to the scene and a big army of people trying to help out," said Brian Hopman, an Associated Press sales associate aboard the flight.

"There was a huge panic," said Hopman, who was seated about halfway back in the plane and reported seeing blood scattered about.

Another traveler, Lucia Tilia, said that once Moreira was restrained, pilots used their belts to tie him down, later allowing him medical attention. "The pilots had to hit him to tie him down," she said.

Argentine authorities said they were investigating whether Moreira was under the influence of drugs or mentally distraught. "He doesn't remember what happened," said Jorge Reta, an Argentine Air Force spokesman.

Late Thursday, Moreira was led by three police officers onto another United flight, which took off for Miami. FBI officials said they expected Moreira to be charged with interfering with a flight crew. Any criminal charges would be filed in the U.S. court district, most likely Miami.

Law enforcement sources say there remains no evidence that Moreira, an employee at a bank in Montevideo, Uruguay, has any ties to known terrorist organizations.

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

The U.S. Department of Transportation gave all airlines until early January to strengthen cockpit doors. Many have done so, and the industry has said it envisions newer and far stronger doors, although they are not yet available.

In Washington, Homeland Security Director Tom Ridge said Moreira did not breach the cockpit. "He tried to gain entry through the bottom of the cockpit door, but it had been a hardened cockpit and he did not," Ridge said in a speech at the National Press Club.

In a recent incidents involving airline security, police removed a disruptive woman from an America West Airlines flight on Jan. 28 that was just about to leave Phoenix for San Diego, officials said.

On Jan. 30, the San Francisco International Airport was evacuated after security guards detected explosives residue on the shoes of a man who then disappeared into a crowd. Thousands of passengers waited outside while 28 gates were closed for about two hours and terminal the United Airlines terminal was searched. The man was not found.

The Associated Press contributed to this report.