The jetliner landed safely in Los Angeles and police took the 80-year-old man, who did not speak English, to a hospital for a 72-hour mental observation, airport spokeswoman Nancy Castles said.
"He evidently started to panic about 15 minutes before landing, when everyone is supposed to be buckled into seats," Castles said.
None of the five crew members or 122 passengers aboard the MD-80 plane from Austin, Texas, reported injuries, American Airlines spokesman Billy Sanez said.
The man hopped out of his seat in coach and marched into first class, Sanez said.
Dr. Robert Rey, a plastic surgeon who practices martial arts, told The Associated Press he got out of his seat and intervened when he heard the man make a "big noise" as he pushed a female flight attendant toward the cockpit.
"When you get a black belt, at that stage your brain just clicks into action," the doctor said. "I restrained this gentleman in a very aggressive way without hurting him."
Another passenger helped as the man kicked and screamed, Rey said. The doctor said he also checked the man's vital signs and determined he was not having a medical emergency.
The flight attendant "was shook up but not hurt," Rey said.
Flight crew members described the man as "very frail," Sanez said. He had been scheduled to board a connecting flight in Singapore after landing in Los Angeles.
Rey, who stars on the E! Network reality show "Dr. 90210" about a Beverly Hills plastic surgeon, was returning home after taping a segment for "The Insider."
Rey also appears as himself on a Carl's Jr. commercial in which he advises a chicken to undergo breast augmentation surgery.