“Upon exiting, he told authorities he had fallen asleep,” the airline said.

The man, an employee of Alaska contractor Menzies Aviation, walked off the plane. He was initially checked by medics at the airport and found to be unhurt, airport spokesman Perry Cooper said.

The man was also checked at a hospital and released, the airline said Monday evening. After his release from the hospital, he passed a drug test, airline spokesman Bryan Zidar said.

The airline did not identify the worker. A Menzies spokesman did not immediately return an email request for comment and details about the employee.

The plane was airborne for 14 minutes.

Seattle’s KING-5 News interviewed passenger Jesse Sycuro who said that first-class passengers had “heard banging from underneath us and a person yelling for help.”

Sycuro said that two air marshals identified themselves and spoke with a flight attendant, who alerted the pilot. “Shortly after that, we heard the announcement that the plane was going to be turned around,” Sycuro said. “The banging continued for quite a while ... Air marshals banged back down trying to communicate with the person in the hold and yelling down that we were landing.”

The trapped man had started work at 5am Monday and was due to finish his shift at 2.30pm, the airline said in a statement. He had been part of a four-person team loading baggage onto the flight, which initially departed at 2.39pm.

Before the plane departed, the leader of the man’s team noticed he was missing, called into the cargo hold for him, and called and texted the man’s cellphone but got no answer, the airline said. Co-workers decided he had finished his shift and gone home.

All ramp employees undergo full criminal background checks and drug checks before hiring and are subject to random drug tests during their employment, the airline statement said.

Passenger Marty Collins told KOMO-TV in Seattle the flight was surrounded by emergency vehicles when it returned to the airport.

She said passengers in her section of the aircraft did not hear the worker banging or making noise. “Nobody knew why we were turning around,” she told the station. “They just said we were fine and we weren’t in any danger.”

Passengers were later told about the situation. The plane carried 170 passengers and six crew members.

“They just said there was someone in the cargo hold and he’s been escorted off and taken away,” she said.

The flight departed again at 3.52pm and arrived at a terminal gate in Los Angeles at 6.29pm, more than an hour late, the airline said.