Two passengers on Flight 320 from Montego Bay, Jamaica, helped subdue the man, identified by the FBI as Ryan Snider.
Terrorism is not suspected, the agency said.
American Airlines spokesman Ed Martelle said the man appeared to be disoriented.
"He did not obey crewmember instructions to sit down and then moved toward the front of the aircraft where he was subdued," he said in a statement.
Passenger Ronald Webb told CNN affiliate WSVN that the incident was disconcerting.
"We were a little bit worried because we didn't know what it was all about," he said.
Snider is expected to make an initial court appearance Tuesday in Miami, the FBI said.