Allison Forburger, who lives in Hawaii, where she works for the Navy, said the man was moving toward the first-class section of the cabin with a blanket over his head when a flight attendant directed him to stop.
As the suspect approached the drink cart at the rear of first class, the flight attendant in economy told him, "Sir, please stop. Sir, I need you to go back to your seat."
Forburger, sitting in an aisle seat at the front of economy class, said other passengers helped the flight attendant get the passenger back toward the back of the plane.
The man did not fight with the other passengers and left a black laptop he had been clutching to his chest on the drink cart, she said.
'Taped him to his chair'
Passenger Lee Lorenzen told CNN affiliate KITV that the flight attendant told the man: "You're not coming in here" and used the cart to block his path.
But Forburger said the cart was already in the way as the flight attendants were picking up dishes from first-class passengers who had just finished lunch.
She recalled the crew member saying, "I need help, I need help, I need to get this guy back to his seat."
She lost sight of the suspect, but Lorenzen told KITV and CNN affiliate KGMB/KHNL the man was duct-taped to a seat.
"It took seconds," Lee Lorenzen told KGMB/KHNL. "He was pushing against the cart and a bunch of guys grabbed him. They found some duct tape. There were pillows and blankets. And they taped him to his chair."
One of the passengers who helped was an off-duty law enforcement officer, the FBI said.
The suspect was met by authorities when the Airbus 321 landed in Honolulu.
"Due to a disturbance during the flight, the crew requested that law enforcement meet the aircraft upon landing in Honolulu," American Airlines said in a statement.
Video from KGMB/KHNL showed two law enforcement officers escorting a person with hands behind their back off the plane.
A user on Instagram posted a video from inside the cabin, showing the person in handcuffs being led down the aisle by a man with "FBI" written on his back.
"Crazy! Someone tried to break into the cockpit on my flight from LA to Honolulu," bplus.noisefloor.dnb wrote. "We were greeted by the FBI. They are now taking us off the plane a few rows at a time for dog sniffing and interviews. I've never seen anything like this."
Crazy! Someone tried to break into the cockpit on my flight from LA to Honolulu. We were greeted by the FBI. They are now taking us off the plane a few rows at a time for dog sniffing and interviews. I've never seen anything like this. #cnn #fbi #usa #homelandsecurity #hawaii #news ----- Any interested news outlets are welcome to use my footage, please credit BPLUS.noisefloor.dnb as the source.
Incident at LAX
The Department of Homeland Security tweeted that the person was detained and the incident appeared to be isolated.
"At this time, there are no other reports of disruptions to flights," the department tweeted. We continue to monitor all flights out of an abundance of caution and will provide updates as necessary."
Earlier, the man, who purchased his ticket around midnight, had an encounter with airport personnel at the airport in Los Angeles, an official briefed on the incident told CNN. The man attempted to use a door off-limits to the public after 3 a.m. PT (6 a.m. ET) while waiting for his flight.
The suspect was cleared to fly after that incident.
The airliner left Los Angeles International Airport at 8:43 a.m. PT (11:43 ET) for the nearly six-hour flight, according to FlightAware.com.
Two F-22 Raptors from the Hawaiian Air National Guard escorted the plane for the final part of the flight, Navy Cmdr. Dave Benham said.