The intercom screeched for flight attendants to help, and I woke up four hours into our flight across South America. 

Red lights were flashing in the cabin. Crew members were running up the aisles to the front of the plane. Passengers craned their necks to get a look at the struggle near the cockpit door. 

The crew seemed confused for a while. They told passengers to stay seated and be calm. 

Then the loudspeaker crackled with a call for doctors or nurses to go the business class cabin. 

I leaned into the aisle to see what was happening as the pilots, crew and several passengers subdued a man. 

The situation seemed to calm down. The crew came back on the intercom to say everything was under control. The flight never turned back. 

Once the plane landed, the crew asked everyone to stay seated. Armed Argentine police dressed in fatigues boarded the plane and took the man away without a struggle. 

They then asked witnesses to stay behind and gather in the first class cabin. Investigators from the FBI and the Federal Aviation Authority took passenger statements. 

When I said I had noticed the man in Miami before we left, officials asked me to tell my story. 

I had seen him as we sat in the United Airlines lounge in Miami awaiting the flight. I smelled cigarette smoke wafting across the nonsmoking room. The smoker turned out to be the same man who caused trouble on the plane. 

I had reported him to airline employees who told him nicely to put out the cigarette. He resisted for about three minutes before complying. 

As we boarded the flight, I notice that the man took a seat in the back of the plan on the right side. 

I apparently was asleep when he moved forward and the altercation broke out. 

First class passengers had a good look at the struggle and one of them was covered with blood. A flight attendant had a bandage on his forearm.