SEATTLE (REUTERS) - A Delta Air Lines flight bound for Beijing returned to Seattle on Thursday (July 6) after a passenger in the first-class cabin assaulted a flight attendant before being subdued by other travellers, a Seattle-Tacoma International Airport spokesman said.

Two people were sent to hospital with non-life-threatening injuries after the Boeing 767-300 landed safely shortly after 7pm, airport spokesman Perry Cooper said.

The unruly male passenger was arrested by Port of Seattle Police Department officers, he added.

Delta flight 129 departed Seattle-Tacoma International Airport at around 5.30pm, but headed back to Seattle roughly 45 minutes into the flight, he said.

Mr Cooper added that the man assaulted a flight attendant in the first-class cabin, but said he had no further details about the incident.

The Federal Bureau of Investigation (FBI) was assisting police with the investigation, said its spokesman Ayn Dietrich.

She added that the FBI was interviewing passengers and had no information to suggest the incident was a threat to national security.

Mr Cooper said multiple passengers intervened to help subdue the suspect during the in-flight disturbance. The pilot decided to turn back and call for police, fire, and medical personnel to meet the plane.

Ms Lorie Dankers, a spokesman for the Transportation Security Administration, said there was no security breach at the airport, south of Seattle.

A representative for Delta Air Lines did not immediately respond to a request for comment.

The Federal Aviation Administration declined to comment.